Android Client does not work after transfer to a new hosting

Very strange bug is happening here:
I have transferred my NC 16.0.1 installation to an new webhoster successfully. I could proof the success by accessing NC as admin and as user successfully and all old data was present and accessible.

Of course, next step is to switch all my clients also to the new server and I started with my Android first. After setting up the new account, it got connection to NC successfully and synced all my contacts successfully. But it does not with the calendar / events and tasks. I have got a long list of error messages in the error.log of the Android DAVx app.

Sorry about my erronous description some minutes before. Clients on desktop computers with Thunderbird / Lightning work flawlessly.

Here some of the messages from the error log from DAVx from my Android.

EXCEPTION:
java.lang.ClassCastException: net.fortuna.ical4j.model.property.XProperty cannot be cast to net.fortuna.ical4j.model.property.Trigger
at net.fortuna.ical4j.model.component.VAlarm.getTrigger(VAlarm.java:302)
at at.bitfire.ical4android.ICalendar$Companion.alarmMinBefore$ical4android_release(ICalendar.kt:131)
at at.bitfire.ical4android.AndroidEvent.insertReminder(AndroidEvent.kt:626)
at at.bitfire.ical4android.AndroidEvent.add(AndroidEvent.kt:401)
at at.bitfire.ical4android.AndroidEvent.add(AndroidEvent.kt:384)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager$processVEvent$1$1.invoke(CalendarSyncManager.kt:179)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager$processVEvent$1$1.invoke(CalendarSyncManager.kt:41)
at at.bitfire.davdroid.syncadapter.SyncManager.useLocal(SyncManager.kt:777)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager$processVEvent$1.invoke(CalendarSyncManager.kt:178)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager$processVEvent$1.invoke(CalendarSyncManager.kt:41)
at at.bitfire.davdroid.syncadapter.SyncManager.useLocal(SyncManager.kt:777)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager.processVEvent(CalendarSyncManager.kt:170)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager.access$processVEvent(CalendarSyncManager.kt:41)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager$downloadRemote$2$1$1.invoke(CalendarSyncManager.kt:144)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager$downloadRemote$2$1$1.invoke(CalendarSyncManager.kt:41)
at at.bitfire.davdroid.syncadapter.SyncManager.useRemote(SyncManager.kt:802)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager$downloadRemote$2$1.invoke(CalendarSyncManager.kt:131)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager$downloadRemote$2$1.invoke(CalendarSyncManager.kt:41)
at at.bitfire.dav4jvm.Response$Companion.parse(Response.kt:211)
at at.bitfire.dav4jvm.DavResource$processMultiStatus$2.invoke(DavResource.kt:465)
at at.bitfire.dav4jvm.DavResource.processMultiStatus(DavResource.kt:484)
at at.bitfire.dav4jvm.DavResource.processMultiStatus(DavResource.kt:435)
at at.bitfire.dav4jvm.DavCalendar.multiget(DavCalendar.kt:151)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager$downloadRemote$2.invoke(CalendarSyncManager.kt:130)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager$downloadRemote$2.invoke(CalendarSyncManager.kt:41)
at at.bitfire.davdroid.syncadapter.SyncManager.useRemote(SyncManager.kt:791)
at at.bitfire.davdroid.syncadapter.SyncManager.useRemoteCollection(SyncManager.kt:812)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager.downloadRemote(CalendarSyncManager.kt:129)
at at.bitfire.davdroid.syncadapter.SyncManager$syncRemote$1$1.run(SyncManager.kt:451)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:428)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
at java.lang.Thread.run(Thread.java:761)

In case, you would see this as a theme, which should be discussed in a forum, driven by the programmers of the Android app, then please let me know. Up to now, I cannot be sure, whether it is on NC side or on the side of the app.

Sorry, it is 32° C outside… :face_with_thermometer:
Even some software seems to play crazy. Fact is, I had to charge my Android. When I took it again, to experiment with the NC syncing, I found to my surprise, that the entire calendar had been synced absolut correctly!!!

I proofed the error log of DAVx but there was none!

Everything is good now, but I cannot tell, what the reason has been for the above described issue. I have nothing changed on my settings!