I'm using DAVdroid version: 1.2.3 together with OwnCloud 9.0.4 to sync calendar and contacts to my Android.
On my PC I have Thunderbird 45.2 with extensions CardBook (for syncinc contacts, https://addons.mozilla.org/de/thunderbird/addon/cardbook/) and Lightning (for syncing calendar.
Since some time I can't sync modified contacts/calender entries to my android anymore.
I already deleted the account from DavDroid and configured it new.
Then the initial sync of calendar and contacts worked without issues.
But when I modify an entry in Thunderbird and sync it to OwnCloud, then I can't sync to android anymore.
In the last months I only added/modified contacts on my android and synced to OwnCloud and Thunderbird in this direction. But a few days ago I modified a contact in Thunderbird and synced it to OwnCloud.
So I don't know since which date or since which update I have this issue.
For further details see attached log files of DavDroid.
[1_1471622935955_contacts.log](Uploading 100%) [0_1471622935955_calendar.log](Uploading 100%)