Google Synchronisation fĂźhrt zu Fehlermeldung

Hallo zusammen,
ich bin neu im Forum und hoffe jemand kann mir weiterhelfen.
Ich habe auf meinem Unraid einen Docker mit Nextcloud installiert und nach Bewältigen der ganzen Konfigurations-Arie habe ich Nextcloud soweit zum laufen gebracht. Nun wollte ich gerne auch meinen Google-Kalender synchronisieren und habe die entsprechende App eingebunden, API erstellt und die Verbindung zum Google Account hergestellt. Klicke ich jedoch dann auf “Kalender importieren” auf einen der Kalender, dann kommt eine Fehlermeldung, die absurderweise lautet ich hätte kein Java installiert.
Schaut man in das Log, dann sieht es allerdings schon deutlich aussagekräftiger aus:

{"reqId":"y1cbyGY8kTJ1GqgXrFQ0","level":3,"time":"2023-04-16T22:33:41+00:00","remoteAddr":"xxx.xxx.xxx.xxx","user":"Name","app":"index","method":"GET","url":"/apps/google_synchronization/import-calendar?calId=Name.Surname%40googlemail.com&calName=Name.Surname%40gmail.com&color=%239a9cff","message":"Class \"Ds\\Set\" not found in file '/config/www/nextcloud/apps/google_synchronization/lib/Service/GoogleCalendarAPIService.php' line 235","userAgent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/112.0","version":"26.0.0.11","exception":{"Exception":"Exception","Message":"Class \"Ds\\Set\" not found in file '/config/www/nextcloud/apps/google_synchronization/lib/Service/GoogleCalendarAPIService.php' line 235","Code":0,"Trace":[{"file":"/config/www/nextcloud/lib/private/AppFramework/App.php","line":183,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->"},{"file":"/config/www/nextcloud/lib/private/Route/Router.php","line":315,"function":"main","class":"OC\\AppFramework\\App","type":"::"},{"file":"/config/www/nextcloud/lib/base.php","line":1055,"function":"match","class":"OC\\Route\\Router","type":"->"},{"file":"/config/www/nextcloud/index.php","line":36,"function":"handleRequest","class":"OC","type":"::"}],"File":"/config/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php","Line":169,"Previous":{"Exception":"Error","Message":"Class \"Ds\\Set\" not found","Code":0,"Trace":[{"file":"/config/www/nextcloud/apps/google_synchronization/lib/Controller/GoogleAPIController.php","line":227,"function":"importCalendar","class":"OCA\\Google\\Service\\GoogleCalendarAPIService","type":"->"},{"file":"/config/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php","line":230,"function":"importCalendar","class":"OCA\\Google\\Controller\\GoogleAPIController","type":"->"},{"file":"/config/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php","line":137,"function":"executeController","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->"},{"file":"/config/www/nextcloud/lib/private/AppFramework/App.php","line":183,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->"},{"file":"/config/www/nextcloud/lib/private/Route/Router.php","line":315,"function":"main","class":"OC\\AppFramework\\App","type":"::"},{"file":"/config/www/nextcloud/lib/base.php","line":1055,"function":"match","class":"OC\\Route\\Router","type":"->"},{"file":"/config/www/nextcloud/index.php","line":36,"function":"handleRequest","class":"OC","type":"::"}],"File":"/config/www/nextcloud/apps/google_synchronization/lib/Service/GoogleCalendarAPIService.php","Line":235},"CustomMessage":"--"}}

Leider fehlen mir die Kenntnisse um zu verstehen warum er diverse Elemente in den .php files nicht finden kann.
Wer kann mir weiterhelfen?