I haven't noticed a pattern yet. In the Nostriches group, we found that we all had different numbers for users in the group. Dropped messages have been confirmed with screenshots, and I've detected dropped messages about 3-5 times from noticing people posting to messages I have not seen.

It sucks, because I really liked the features that were promoted, and now I can't trust it as a communication tool. I definetly cannot recommend it to others. 😥