On multiple customer environments running Domino on Windows Server 2016 you always receive the mentioned error when trying to delete a database.
One customer also had issues by accessing the FT index of databases after the Domino V10 migration.
First I thought that running the Domino servers in a clustered environment caused this issue but it´s much more easier:
Just exclude the Domino Data directory from being scanned by the Windows Defender. Afterwards everything´s running fine and you also are able to delete databases.
Right now I received the information from Uli that there´s a known bug in 10.0.1+ where DAOSMgr is not releasing database handles after running a “resync” or a “resync force”. But there´s a HotFix for 10.0.1 FP1 with SPR # GFALBCFAK3. So it seems that this fix is not included in 10.0.1 FP2 ( fix list ) because the fix was released just the day before FP2.