I had an old 10.2 version connected to active directory, then I installed a new 10.3 version with auto migration enabled.
I encountered 2 problems :
1- nonmain calendars are not shown. But I checked in ftp they are imported and available.
2- in old server sometimes "account not found locally"error is shown denying the user which resolves in a few seconds even when logging on old server. I checked active directory error logs and no problem is reported there.
Please report these issues via the support channel (if you have a valid subscription) as that is the right channel to investigate them.