[j-nsp] Configuration database stuck with mgd crashing

[Tore Anderson]

One of my routers (a MX240 running 16.1R6-S2.3) have gotten stuck in a
state where it believes the configuration database has been modified,
and if I try to configure it anyway, mgd crashes and is respawned:

tore at router> configure exclusive 
error: configuration database modified

tore at router> configure private      
error: shared configuration database modified

tore at router> configure 
Entering configuration mode

Message from syslogd at router at Aug 31 13:38:57  ...
router mgd[20554]: ../../../../../../src/ui/lib/access/model.c:238: insist 'model > 0 && model <= MODEL_MAX' failed

error: session failure: unexpected termination
error: remote side unexpectedly closed connection
Connection to router closed.

At this point PID 20554 goes away from the process list. However if I
log back in I can see a «ghost» reference to it:

router> configure exclusive 
Users currently editing the configuration:
  tore terminal pts/0 (pid 20554) on since 2018-08-31 13:38:57 CEST, idle 00:01:25
error: configuration database modified

"request system logout user tore all" will get rid of that reference,
but the fundamental defective state of the configuration database
remains.

Any suggestions on how to correct this problem without requiring
any downtime? I have of course tried "restart management", but 
that didn't help. NETCONF is impacted too.

Tore