As of your case, in vary rare case pool is unable to identify finder for certain block(could be various reasons, wallet RPC gets stuck, some occasional restart is needed then) in such cases we consider block as mine in shared mode and distribute proportionally.
So now the end of more than 2 week of mining at 120 mhs each with 2 miner (so 240mhs ) is only a "sorry the block is divided by every miner on pool"??
I'm not sure this is the right answer.
Agreed. It's a serious issue even if only rare. If it can't be prevented it should be corrected manually
once reported.