I had an issue after switching dav-syncprovider in Android (CM 12.1 nightly) from dmfs ( https://play.google.com/store/apps/developer?id=Marten+Gajda ) to DAVdroid ( https://f-droid.org/repository/browse/?fdid=at.bitfire.davdroid ).
Some of the contacts did not show up on my Android-device.
Apparently this was a known bug with some incorrectly formated contacts which DMFS supports/handles, but DAVdroid does not.
The solution was to export the contacts, and then re-import them via the wizard in Contacts-app in Android.
This gave me back all my contacts, but…
Pictures were gone.
After a bunch of searching, testing and anxiety I stumpled upon this:
https://github.com/bitfireAT/davdroid/issues/53#issuecomment-39617581
So, Android in version 4.3.1 only support importing vCard 2.1, but my .vcf-file was a vCard 3-file.
I’m guessing Android 5.1.1 is not much better.
I tried alot of things, but after reading these three issues I gave up for now. Back to DMFS untill either DAVdroid implements workaround, or owncloud starts working as it should do (because it was apparently OwnCloud’s fault.)
https://github.com/owncloud/contacts/issues/979
https://github.com/bitfireAT/davdroid/issues/578
https://github.com/bitfireAT/davdroid/issues/508
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