Hi,
I have a similar problem but with different trace and I get it with v1.7.2-gplay.
Trace:
EXCEPTION:
java.lang.NoClassDefFoundError: java.util.Objects
at net.fortuna.ical4j.model.TimeZoneRegistryImpl$ZoneOffsetKey.equals(TimeZoneRegistryImpl.java:473)
at java.util.HashMap.get(HashMap.java:306)
at net.fortuna.ical4j.model.TimeZoneRegistryImpl.addTransitions(TimeZoneRegistryImpl.java:424)
at net.fortuna.ical4j.model.TimeZoneRegistryImpl.generateTimezoneForId(TimeZoneRegistryImpl.java:339)
at net.fortuna.ical4j.model.TimeZoneRegistryImpl.loadVTimeZone(TimeZoneRegistryImpl.java:253)
at net.fortuna.ical4j.model.TimeZoneRegistryImpl.getTimeZone(TimeZoneRegistryImpl.java:212)
at at.bitfire.ical4android.MiscUtils.androidifyTimeZone(MiscUtils.kt:30)
at at.bitfire.ical4android.AndroidEvent.buildEvent(AndroidEvent.kt:470)
at at.bitfire.davdroid.resource.LocalEvent.buildEvent(LocalEvent.kt:76)
at at.bitfire.ical4android.AndroidEvent.add(AndroidEvent.kt:370)
at at.bitfire.ical4android.AndroidEvent.add(AndroidEvent.kt:357)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager.processVEvent(CalendarSyncManager.kt:201)
at at.bitfire.davdroid.syncadapter.CalendarSyncManager.downloadRemote(CalendarSyncManager.kt:164)
at at.bitfire.davdroid.syncadapter.SyncManager.performSync(SyncManager.kt:154)
at at.bitfire.davdroid.syncadapter.CalendarsSyncAdapterService$SyncAdapter.sync(CalendarsSyncAdapterService.kt:54)
at at.bitfire.davdroid.syncadapter.SyncAdapterService$SyncAdapter.onPerformSync(SyncAdapterService.kt:62)
at android.content.AbstractThreadedSyncAdapter$SyncThread.run(AbstractThreadedSyncAdapter.java:254)
Just like with @varac there is TZID=PST
but no VTIMEZONE
.
It’s a work calendar so I can’t include it directly here.
The server is running GroupWise which is not developed anymore so there’s no option for server-side fixes 
Any ideas?