Fair point that we will need more info about this, problem is that info doesn't exist .-.These are a couple questions I can think of off the top of my head that should help iron out what's wrong with the XP levels:
What were the players doing before they realized the XP levels had disappeared?
When did the players notice their XP levels were disappearing?
Now what do I think is wrong with them is that usually when you go from survival to creative and back. You end up losing XP levels so this means you guys could be losing them when you go from a survival round to a classic round and then back but that's just speculation on my end :3 but getting answers to those questions should give us a more in-depth as to what's happening.
Yea. I played a creative round last night and I still have all my XP levels so it's not the transfer from survival to classic rounds and back that is causing the issue so I have no idea what isJust a little input - I've been losing mine for a couple of months. I've not really cared all that much though so I've just left it. Now that there are other players that are mentioning it as well, I might as well.
Also, std1997 I don't think it would be creative (possible, though) as I started losing it well before the classic rounds were introduced. Not denying the possibility, though.