db5 / PANIC errors under 2.5.12?

[Karl Pielorz]

--On 12 November 2018 at 08:40:39 +0000 Karl Pielorz 
<kpielorz_lst at tdx.co.uk> wrote:

> It'll be a few weeks now (typically) before this happens again.

This just happened again - but doesn't appear to be related to connections 
we just had logged:

"
Nov 15 18:31:00 imap[84552]: DBERROR db5: pthread suspend failed: Invalid 
argument
Nov 15 18:31:00 imap[84552]: DBERROR db5: BDB0061 PANIC: Invalid argument
Nov 15 18:31:00 imap[84552]: DBERROR: critical database situation
...
Nov 15 18:31:00 imap[84554]: DBERROR db5: BDB0060 PANIC: fatal region error 
detected; run recovery
"

Again, shutdown, clear out 'db/*' and restart - and it's back. The files 
'db':

-rw-------  1 cyrus  cyrus  14770176 Nov 15 19:14 __db.001
-rw-------  1 cyrus  cyrus     32768 Nov 15 19:14 __db.002
-rw-------  1 cyrus  cyrus     49152 Nov 15 19:14 __db.003
-rw-------  1 cyrus  cyrus         4 Nov 15 19:14 skipstamp

Appear to just be 'binary' - i.e. 'files' against them shows binary - are 
these really the files likely to be causing the problem?

Or is the 'DBERROR db5' still relating to a .db file somewhere? - Be handy 
if the 'fatal region' error [or any of them] could list the file the 
problem is in :)

Just really looking for any hints where to look next...

-Karl