[Samba] 'samba-tool domain tombstones expunge' fails to remove expired tombstones

[miguel medalha]

On a particular DC, running 'samba-tool dbcheck' produces the following:

     NOTICE: found 2 expired tombstones, 'samba' will remove them daily, 
'samba-tool domain tombstones expunge' would do that immediately.

When I run 'samba-tool domain tombstones expunge' the following is produced:

     Removed 0 objects and 0 links successfully

Running 'samba-tool dbcheck' again shows that the 2 expired tombstones 
are still there.

What should I do to force their removal? This happened after upgrading 
to samba 4.10.x. Reverting to 4.8.11 solves other problems (coming from 
Python 2.6), but not this one.