I have been using DavDroid for quite some time. Some time ago it started throwing errors after each sync, albeit the syncs themselves succeed (or at least I haven’t found any difference between the server and my device yet).
The device in question is a Samsung S4 mini, running Android 4.4.2.
The relevant parts of the logcat output are as follows (filtered by egrep davdroid\|HttpClient\|Wire

I/davdroid.SyncManager(22907): Full synchronization forced
I/davdroid.SyncManager(22907): Fetching remote resource list
W/aCalendar( 3072): unknown calendar type bitfire.at.davdroid [...]
W/aCalendar( 3072): unknown calendar type bitfire.at.davdroid [...]
W/aCalendar( 3072): unknown calendar type bitfire.at.davdroid [...]
V/davdroid.URIUtils(22907): Normalized URI [...]
D/davdroid.WebDavResource(22907): Processing multi-status element [...]
The last two lines are repeated 4170 times, if I count it right.
E/davdroid.resource(22907): Ignoring unparseable entity in multi-response
E/davdroid.resource(22907): at.bitfire.davdroid.resource.InvalidResourceException: No VEVENT without RECURRENCE-ID found
E/davdroid.resource(22907): at at.bitfire.davdroid.resource.Event.parseEntity(Event.java:131)
E/davdroid.resource(22907): at at.bitfire.davdroid.resource.WebDavCollection.multiGet(WebDavCollection.java:121)
E/davdroid.resource(22907): at at.bitfire.davdroid.syncadapter.SyncManager.pullNew(SyncManager.java:195)
E/davdroid.resource(22907): at at.bitfire.davdroid.syncadapter.SyncManager.synchronize(SyncManager.java:95)
E/davdroid.resource(22907): at at.bitfire.davdroid.syncadapter.DavSyncAdapter.onPerformSync(DavSyncAdapter.java:138)
E/davdroid.resource(22907): at android.content.AbstractThreadedSyncAdapter$SyncThread.run(AbstractThreadedSyncAdapter.java:259)
The block is repeated 18 times.
I/davdroid.SyncManager(22907): Fetching 0 updated remote resource(s)
I/davdroid.SyncManager(22907): Removing entries that are not present remotely anymore (retaining 4151 entries)
D/davdroid.Collection(22907): Committing 2 operations ...
E/davdroid.DavSyncAdapter(22907): Local storage (content provider) exception
E/davdroid.DavSyncAdapter(22907): at.bitfire.davdroid.resource.LocalStorageException: Couldn't access local content provider
E/davdroid.DavSyncAdapter(22907): at at.bitfire.davdroid.resource.LocalCollection.commit(LocalCollection.java:382)
E/davdroid.DavSyncAdapter(22907): at at.bitfire.davdroid.resource.LocalCalendar.deleteAllExceptRemoteNames(LocalCalendar.java:268)
E/davdroid.DavSyncAdapter(22907): at at.bitfire.davdroid.syncadapter.SyncManager.synchronize(SyncManager.java:99)
E/davdroid.DavSyncAdapter(22907): at at.bitfire.davdroid.syncadapter.DavSyncAdapter.onPerformSync(DavSyncAdapter.java:138)
E/davdroid.DavSyncAdapter(22907): at android.content.AbstractThreadedSyncAdapter$SyncThread.run(AbstractThreadedSyncAdapter.java:259)
E/davdroid.DavSyncAdapter(22907): Caused by: android.os.TransactionTooLargeException
E/davdroid.DavSyncAdapter(22907): at android.os.BinderProxy.transact(Native Method)
E/davdroid.DavSyncAdapter(22907): at android.content.ContentProviderProxy.applyBatch(ContentProviderNative.java:510)
E/davdroid.DavSyncAdapter(22907): at android.content.ContentProviderClient.applyBatch(ContentProviderClient.java:377)
E/davdroid.DavSyncAdapter(22907): at at.bitfire.davdroid.resource.LocalCollection.commit(LocalCollection.java:372)
E/davdroid.DavSyncAdapter(22907): ... 4 more
I/davdroid.DavSyncAdapter(22907): Sync complete for com.android.calendar
Any idea what might be going on?
–jtg