[Samba] 'samba-tool dbcheck' reports only a "Bus error"

[Ole Traupe]

For a few days now my primary DC has some issues. I can create users 
without a problem. But when I try to alter the group membership of 
users, one of my samba processes crashes (the one listening to the LDAP 
related ports: 389, 636, 3268, 3269).

Also, when I start my backup DC, a few seconds later another process 
crashes on the primary DC (the RPC related listening to 135 and 1024).

I haven't made any updates to OS or Samba (still 4.2.2), but I have 
adjusted some UIDs and GIDs recently.

Despite "log level = 3", the "log.samba" gives only this,

[2015/10/22 19:05:46.500567,  0] ../lib/util/fault.c:78(fault_report)
   ===============================================================
[2015/10/22 19:05:46.515490,  0] ../lib/util/fault.c:79(fault_report)
   INTERNAL ERROR: Signal 7 in pid 3794 (4.2.2)
   Please read the Trouble-Shooting section of the Samba HOWTO
[2015/10/22 19:05:46.515633,  0] ../lib/util/fault.c:81(fault_report)
   ===============================================================
[2015/10/22 19:05:46.515732,  0] ../lib/util/fault.c:151(smb_panic_default)
   PANIC: internal error

while the trouble shooting page directs me to the log files. ;)

When I try a 'samba-tool dbcheck' on the PDC, I get the message "Bus 
error". Nothing more. When I do it on the BDC, the check runs through 
without errors. The sam.ldb on the BDC is in an earlier state because 
replication isn't working any more.

What does "Bus error" mean? Have I messed up my data base? Or is it 
something else?

What can I do?

Ole