"Refresh server list" error-code ignored by some versions of the Mollom module

We recently changed the load-balancing behavior of the Mollom server, where we now ask all the clients to update their server lists (error-code 1100) every 30 minutes (instead of almost never before). We have received multiple bug reports of people that were not possible to contact any Mollom server after this change.

This is because certain versions of the Mollom module appear to ignore the "error 1100" they receive by the Mollom server, and connect directly to the next server in their server list, issuing the same API call, instead of (what they ought to do) directly request a new server list. Because they keep issuing the original API calls, all servers keep returning the "error 1100", resulting in an "all Mollom servers are not available"-error. The module then falls back to its fall-back behavior of just letting all comments in, or blocking all of them.

This issue should be solved in the latest Mollom module versions which implements the updated flow as detailed in our latest API documentation (but this should also be double-checked). We need to identify which versions of the module are susceptible to this problem, and the people using this module should be urged to upgrade, as this critical issue makes the Mollom module completely unusable.

We temporarily reverted the server's changes, not returning the "error 1100" for now. A related issue is #322951: Misleading errors in watchdog.