I’m using version 0.6.2 from F-Droid on a Samsung Galaxy S4 mini running Samsung stock firmware (based on Android 4.2.2). DAVdroid is connected to my ownCloud 7 server to sync contacts and calendars.
I have set up speed dials in the standard (Samsung?) dialer app. If I now update a contact in ownCloud (in my case the picture) and synchronize my phone, the speed dials referencing that contact are lost. Not sure whether this is a problem of DAVdroid, which might delete and then create a changed account instead of updating it or whether it is a bug in the dialer.