Open directory server crashing every 30 days / clients unable to connect to calendar, contacts server

Question

Hello everyone,
I am running an up to date Mavericks Server which serves exclusively as a calendar and contacts server for about two dozens devices. The server is reachable via DynDNS, however, the public IP hardly ever changes (only once or twice a year maybe). Tried setting the OS X DNS Server to serve "all clients" and "some clients".
For about 6 months (i.e. also under Mountain Lion), I am having a very strange problem. Roughly every 20-30 days, clients will not be able to connect to the server, instead getting a "wrong password" dialog. Restarting the open directory server will help for the next 30 days.
I have tried repairing the database as detailed here, however, the issue persists.
Any help would be highly appreciated!
I would have tried setting up a clean server installation, migrating calendars/contacts manually and re-adding all users by hand, however, I am not aware of an easy way to do so. The terminal command for calendar backup is broken under mavericks (might work with this workaround) and re-adding users manually would apparently involve correcting user UUIDs afterwards in order to match the migrated calendar data. Do you know of a better approach?
Thanks a lot!
DPSG-Scout

Answer 1

Hi Linc,
This looks the most relevant to me:
opendirectory.log
2014-03-11 11:13:09.460675 CET - 333.2628758.2628759 - Client: Python, UID: 93, EUID: 93, GID: 93, EGID: 93
2014-03-11 11:13:09.460675 CET - 333.2628758.2628759, Node: /Local/Default, Module: PlistFile - predicates with 'AND' are not supported
2014-03-11 12:09:00.296514 CET - State information (some requests have been active for extended period):
          Sessions: {
              28 -- opendirectoryd:
                          Session ID: 7BFBA6FE-A968-4399-A129-E3A5945E2A81
                          Refs: singleton
                          Type: Default
                          Target: localhost
          Nodes: {
              43 -- authd:
                          Node ID: 6D0E236D-6DBD-4E8C-BC01-B3F50C2C2D8E
                          Nodename: /LDAPv3/127.0.0.1
                          Session ID: <Default>
                          Refs: 1
                          Internal Use: X
an many more similar ones…
Thanks for your effort!