replication fails after 2.3.9 -> 2.3.11

[Paul Dekkers]

Hi,

I finally found a moment for upgrading my 2.3.9 install (using Simon's
RPMs on Red Hat 4.6, 64-bit) to 2.3.11-3 (leaving the config files
untouched), after which it seems that replication isn't working properly
anymore.

If I run the sync_client, just a simple -u paul, I see in my logs:

sync_client[18493]: SETMODSEQ received BAD response: Syntax error in
Setflags: Invalid modseq
sync_client[18493]: Error in do_user(paul): bailing out!

Before the upgrade, I'm sure replication was working properly. I
checked, both servers are really running the same versions of everything.

I noticed that if I strace the sync_client, the folder on which it bails
out is always the same. If I reconstruct that folder, and re-run (or
just the mailbox), the process continues (up to the next folder that
causes the thing to bail out - although it doesn't bail out on every
folder).

There were more strange log-items related to the sync_client;

sync_client[18232]: USER: Invalid type 1 response from server
sync_client[18232]: Discarding: 0000000000000000000000000000000000000000 ()
sync_client[18232]: Discarding: 2 0
0000000000000000000000000000000000000000 ()
sync_client[18232]: Discarding: 3 0
0000000000000000000000000000000000000000 ()
sync_client[18232]: Discarding: 4 0
0000000000000000000000000000000000000000 (\answered)
sync_client[18232]: Discarding: 5 0
0000000000000000000000000000000000000000 ()

and a bunch more, like:

sync_client[18232]: Discarding: archief.thuispc
...
sync_client[18232]: sync_eatlines_unsolicited(): resynchronised okay
...
sync_client[18232]: Processing sync log file
/data/config/imap/sync/log-18231 failed: Bad protocol
sync_client[18231]: process 18232 exited, status 1

Any clue why replication stopped working properly for me after the upgrade?

Paul