Right now, the only way I can see to do this is to delete the account and re-create it. This is a horrible usability problem.
Thanks for your report, but this is a duplicate of #219.
Thanks for your report, but this is a duplicate of #230. Please follow up there.
Thanks for reporting the issue. This is probably a duplicate of #186, please follow up there.
I have now reproduced the problem on Android 7.0 in the SDK emulator image:
However, I couldn’t see any differences between DAVdroid versions. I have tested DAVdroid 184.108.40.206 and DAVdroid 1.2.2 with Android 7.0, and it does’t work, too (as I have suspected).
So, in my tests, this is the Android 7.0 bug which has been fixed in Android 7.1 and is not related to DAVdroid.
I don’t have an explanation why different DAVdroid versions have behaved differently in your environment / testing setup.