diff --git a/CHANGELOG.md b/CHANGELOG.md
index 475f4995b..08a63c734 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,7 @@
 # Changelog Fab-manager
 
+- Fix a bug: unable to show machine availability slot for admin
+
 ## v5.3.9 2022 April 01
 
 - Optimise sql query, avoid to N+1
diff --git a/app/frontend/src/javascript/directives/cart.js b/app/frontend/src/javascript/directives/cart.js
index da8865547..968b169e7 100644
--- a/app/frontend/src/javascript/directives/cart.js
+++ b/app/frontend/src/javascript/directives/cart.js
@@ -564,7 +564,12 @@ Application.Directives.directive('cart', ['$rootScope', '$uibModal', 'dialogs',
               return dialogs.confirm({
                 templateUrl: '/shared/confirm_modify_slot_modal.html',
                 resolve: {
-                  object () { return $scope.slot; }
+                  object () {
+                    if ($scope.slot.user && !$scope.slot.user.name) {
+                      $scope.slot.user.name = _t('app.shared.confirm_modify_slot_modal.deleted_user');
+                    }
+                    return $scope.slot;
+                  }
                 }
               }
               , function (type) {
diff --git a/app/frontend/templates/admin/calendar/calendar.html b/app/frontend/templates/admin/calendar/calendar.html
index c760602ef..637579fca 100644
--- a/app/frontend/templates/admin/calendar/calendar.html
+++ b/app/frontend/templates/admin/calendar/calendar.html
@@ -80,7 +80,8 @@
       <div class="widget-content no-bg auto wrapper" ng-class="{'reservations-locked': availability.lock}">
         <ul class="list-unstyled" ng-if="reservations.length > 0">
           <li ng-repeat="r in reservations" class="m-b-xs" ng-class="{'reservation-canceled':r.canceled_at}">
-            {{r.user.name}}
+            <span ng-if="r.user.name">{{r.user.name}}</span>
+            <span translate ng-if="!r.user.name">{{ 'app.admin.calendar.deleted_user' }}</span>
               - <span class="label reservation-time">{{ r.start_at | amDateFormat:'LLL' }} - {{ r.end_at | amDateFormat:'LT' }}</span>
               - <span class="label label-success text-white">{{r.reservable.name}}</span>
               <span class="btn btn-warning btn-xs" ng-click="cancelBooking(r)" ng-if="!r.canceled_at"><i class="fa fa-times red"></i></span>
diff --git a/app/frontend/templates/shared/confirm_modify_slot_modal.html b/app/frontend/templates/shared/confirm_modify_slot_modal.html
index eb17c8d0b..bc78c162a 100644
--- a/app/frontend/templates/shared/confirm_modify_slot_modal.html
+++ b/app/frontend/templates/shared/confirm_modify_slot_modal.html
@@ -3,8 +3,8 @@
   <h1 translate>{{ 'app.shared.confirm_modify_slot_modal.change_the_slot' }}</h1>
 </div>
 <div class="modal-body">
-  <p ng-show="currentUser.id === object.user.id" translate>{{ 'app.shared.confirm_modify_slot_modal.do_you_want_to_change_your_booking_slot_initially_planned_at' }} </p>
-  <p ng-show="currentUser.id !== object.user.id" translate translate-values="{NAME: object.user.name}">{{ 'app.shared.confirm_modify_slot_modal.do_you_want_to_change_NAME_s_booking_slot_initially_planned_at' }}</p>
+  <p ng-show="!object.user" translate>{{ 'app.shared.confirm_modify_slot_modal.do_you_want_to_change_your_booking_slot_initially_planned_at' }} </p>
+  <p ng-show="object.user && currentUser.id !== object.user.id" translate translate-values="{NAME: object.user.name}">{{ 'app.shared.confirm_modify_slot_modal.do_you_want_to_change_NAME_s_booking_slot_initially_planned_at' }}</p>
   <p><strong>{{object.start | amDateFormat: 'LL'}} : {{object.start | amDateFormat:'LT'}} - {{object.end | amDateFormat:'LT'}}</strong></p>
 </div>
 <div class="modal-footer">
diff --git a/app/views/api/availabilities/machine.json.jbuilder b/app/views/api/availabilities/machine.json.jbuilder
index 6570c03fe..ab4879c08 100644
--- a/app/views/api/availabilities/machine.json.jbuilder
+++ b/app/views/api/availabilities/machine.json.jbuilder
@@ -18,8 +18,8 @@ json.array!(@slots) do |slot|
   # the user who booked the slot, if the slot was reserved
   if (%w[admin manager].include? @current_user_role) && slot.reservation
     json.user do
-      json.id slot.reservation.user.id
-      json.name slot.reservation.user.profile.full_name
+      json.id slot.reservation.user&.id
+      json.name slot.reservation.user&.profile&.full_name
     end
   end
   json.tag_ids slot.availability.tag_ids
diff --git a/app/views/api/availabilities/spaces.json.jbuilder b/app/views/api/availabilities/spaces.json.jbuilder
index cbf35860e..5661bdd35 100644
--- a/app/views/api/availabilities/spaces.json.jbuilder
+++ b/app/views/api/availabilities/spaces.json.jbuilder
@@ -19,8 +19,8 @@ json.array!(@slots) do |slot|
   # the user who booked the slot, if the slot was reserved
   if (%w[admin manager].include? @current_user_role) && slot.reservation
     json.user do
-      json.id slot.reservation.user.id
-      json.name slot.reservation.user.profile.full_name
+      json.id slot.reservation.user&.id
+      json.name slot.reservation.user&.profile&.full_name
     end
   end
   json.tag_ids slot.availability.tag_ids
diff --git a/app/views/api/reservations/_reservation.json.jbuilder b/app/views/api/reservations/_reservation.json.jbuilder
index b2be48b4b..402fb765d 100644
--- a/app/views/api/reservations/_reservation.json.jbuilder
+++ b/app/views/api/reservations/_reservation.json.jbuilder
@@ -2,7 +2,7 @@
 
 json.id reservation.id
 json.user_id reservation.statistic_profile.user_id
-json.user_full_name reservation.user.profile.full_name
+json.user_full_name reservation.user&.profile&.full_name
 json.message reservation.message
 json.slots_attributes reservation.slots do |s|
   json.id s.id
diff --git a/config/locales/app.admin.de.yml b/config/locales/app.admin.de.yml
index 413b5e61f..e4ee36203 100644
--- a/config/locales/app.admin.de.yml
+++ b/config/locales/app.admin.de.yml
@@ -109,6 +109,7 @@ de:
         slots: "Slots"
         slots_of: "von"
         minutes: "Minuten"
+        deleted_user: "Deleted user"
       #import external iCal calendar
       icalendar:
         icalendar_import: "iCalendar Import"
diff --git a/config/locales/app.admin.en.yml b/config/locales/app.admin.en.yml
index f2e58f01d..3efdde47f 100644
--- a/config/locales/app.admin.en.yml
+++ b/config/locales/app.admin.en.yml
@@ -109,6 +109,7 @@ en:
         slots: "slots"
         slots_of: "of"
         minutes: "minutes"
+        deleted_user: "Deleted user"
       # import external iCal calendar
       icalendar:
         icalendar_import: "iCalendar import"
diff --git a/config/locales/app.admin.es.yml b/config/locales/app.admin.es.yml
index 995b97e9b..b95da21ba 100644
--- a/config/locales/app.admin.es.yml
+++ b/config/locales/app.admin.es.yml
@@ -109,6 +109,7 @@ es:
         slots: "slots"
         slots_of: "of"
         minutes: "minutes"
+        deleted_user: "Deleted user"
       #import external iCal calendar
       icalendar:
         icalendar_import: "iCalendar import"
diff --git a/config/locales/app.admin.fr.yml b/config/locales/app.admin.fr.yml
index 0185b4aff..1d21da59a 100644
--- a/config/locales/app.admin.fr.yml
+++ b/config/locales/app.admin.fr.yml
@@ -109,6 +109,7 @@ fr:
         slots: "créneaux"
         slots_of: "de"
         minutes: "minutes"
+        deleted_user: "Utilisateur supprimé"
       #import external iCal calendar
       icalendar:
         icalendar_import: "Import iCalendar"
diff --git a/config/locales/app.admin.no.yml b/config/locales/app.admin.no.yml
index 672626240..3100001f7 100644
--- a/config/locales/app.admin.no.yml
+++ b/config/locales/app.admin.no.yml
@@ -109,6 +109,7 @@
         slots: "reservasjoner"
         slots_of: "av"
         minutes: "minutter"
+        deleted_user: "Deleted user"
       #import external iCal calendar
       icalendar:
         icalendar_import: "iCalendar import"
diff --git a/config/locales/app.admin.pt.yml b/config/locales/app.admin.pt.yml
index dfa8991af..469f9c2a8 100755
--- a/config/locales/app.admin.pt.yml
+++ b/config/locales/app.admin.pt.yml
@@ -109,6 +109,7 @@ pt:
         slots: "slots"
         slots_of: "do"
         minutes: "minutos"
+        deleted_user: "Deleted user"
       #import external iCal calendar
       icalendar:
         icalendar_import: "importar iCalendar"
diff --git a/config/locales/app.admin.zu.yml b/config/locales/app.admin.zu.yml
index 1641ab695..67541d8e0 100644
--- a/config/locales/app.admin.zu.yml
+++ b/config/locales/app.admin.zu.yml
@@ -109,6 +109,7 @@ zu:
         slots: "crwdns20302:0crwdne20302:0"
         slots_of: "crwdns20304:0crwdne20304:0"
         minutes: "crwdns20288:0crwdne20288:0"
+        deleted_user: "Deleted user"
       #import external iCal calendar
       icalendar:
         icalendar_import: "crwdns6855:0crwdne6855:0"
diff --git a/config/locales/app.shared.de.yml b/config/locales/app.shared.de.yml
index 5690b9b2f..c6c5c9b1c 100644
--- a/config/locales/app.shared.de.yml
+++ b/config/locales/app.shared.de.yml
@@ -283,6 +283,7 @@ de:
         do_you_want_to_change_NAME_s_booking_slot_initially_planned_at: "Möchten Sie den {NAME}-Buchungsplatz ändern? Ursprünglich geplant um:"
         cancel_this_reservation: "Reservierung stornieren"
         i_want_to_change_date: "Ich möchte das Datum ändern"
+        deleted_user: "Deleted user"
       #user public profile
       public_profile:
         last_activity_html: "Letzte Aktivität <br><strong>am {DATE}</strong>"
diff --git a/config/locales/app.shared.en.yml b/config/locales/app.shared.en.yml
index 6f647d6fc..b7f029d88 100644
--- a/config/locales/app.shared.en.yml
+++ b/config/locales/app.shared.en.yml
@@ -283,6 +283,7 @@ en:
         do_you_want_to_change_NAME_s_booking_slot_initially_planned_at: "Do you want to change {NAME}'s booking slot, initially planned at:"
         cancel_this_reservation: "Cancel this reservation"
         i_want_to_change_date: "I want to change date"
+        deleted_user: "deleted user"
       #user public profile
       public_profile:
         last_activity_html: "Last activity <br><strong>on {DATE}</strong>"
diff --git a/config/locales/app.shared.es.yml b/config/locales/app.shared.es.yml
index 692915093..e1212c6bb 100644
--- a/config/locales/app.shared.es.yml
+++ b/config/locales/app.shared.es.yml
@@ -283,6 +283,7 @@ es:
         do_you_want_to_change_NAME_s_booking_slot_initially_planned_at: "Desea cambiar la reserva de {NAME} , efectuada inicialmente el:"
         cancel_this_reservation: "Cancelar reserva"
         i_want_to_change_date: "Quiero cambiar la fecha"
+        deleted_user: "deleted user"
       #user public profile
       public_profile:
         last_activity_html: "Last activity <br><strong>on {DATE}</strong>"
diff --git a/config/locales/app.shared.fr.yml b/config/locales/app.shared.fr.yml
index 4ddfca19f..2247bef6f 100644
--- a/config/locales/app.shared.fr.yml
+++ b/config/locales/app.shared.fr.yml
@@ -283,6 +283,7 @@ fr:
         do_you_want_to_change_NAME_s_booking_slot_initially_planned_at: "Souhaitez-vous changer le créneau de réservation de {NAME}, initialement prévu au :"
         cancel_this_reservation: "Annuler cette réservation"
         i_want_to_change_date: "Je veux changer de date"
+        deleted_user: "l'utilisateur supprimé"
       #user public profile
       public_profile:
         last_activity_html: "Dernière activité <br><strong>le {DATE}</strong>"
diff --git a/config/locales/app.shared.no.yml b/config/locales/app.shared.no.yml
index b241457f0..5076413cd 100644
--- a/config/locales/app.shared.no.yml
+++ b/config/locales/app.shared.no.yml
@@ -283,6 +283,7 @@
         do_you_want_to_change_NAME_s_booking_slot_initially_planned_at: "Vil du endre {NAME} sin bestillingsplass, som opprinnelig er planlagt på:"
         cancel_this_reservation: "Avbryt reservasjon"
         i_want_to_change_date: "Jeg vil endre dato"
+        deleted_user: "deleted user"
       #user public profile
       public_profile:
         last_activity_html: "Siste aktivitet <br><strong>{DATE}</strong>"
diff --git a/config/locales/app.shared.pt.yml b/config/locales/app.shared.pt.yml
index 2e85e3b1a..1979341cb 100755
--- a/config/locales/app.shared.pt.yml
+++ b/config/locales/app.shared.pt.yml
@@ -283,6 +283,7 @@ pt:
         do_you_want_to_change_NAME_s_booking_slot_initially_planned_at: "Você deseja alterar o agendamento do usuário {NAME}, inicialmente marcado para:"
         cancel_this_reservation: "Cancelar essa reserva"
         i_want_to_change_date: "Eu quero alterar a data"
+        deleted_user: "deleted user"
       #user public profile
       public_profile:
         last_activity_html: "Última atividade <br><strong>em {DATE}</strong>"
diff --git a/config/locales/app.shared.zu.yml b/config/locales/app.shared.zu.yml
index b5bb13608..bdfd31a34 100644
--- a/config/locales/app.shared.zu.yml
+++ b/config/locales/app.shared.zu.yml
@@ -283,6 +283,7 @@ zu:
         do_you_want_to_change_NAME_s_booking_slot_initially_planned_at: "crwdns9825:0{NAME}crwdne9825:0"
         cancel_this_reservation: "crwdns9827:0crwdne9827:0"
         i_want_to_change_date: "crwdns9829:0crwdne9829:0"
+        deleted_user: "deleted user"
       #user public profile
       public_profile:
         last_activity_html: "crwdns9843:0{DATE}crwdne9843:0"