It does happen that we lose data for users, due to lack of error handling with the API to Groundspeak servers. This is probably our fault but we have not managed to find the reason yet.
It's happening to about 0-10 geocachers per day (of almost 5 million). It is however a bit more likely for the users of the site and those with a lot of finds.
Since we are aware of it, we often repair this within hours of it happening, otherwise it normally repairs itself within 24-30 hours.