This has been happening on and off for a week now and seemingly at random. Me and my friends are on a realm and at random points the server becomes laggy, disconnects us, and then when reconnect it has essentially rewinded the server in time by 15-30 minutes. Just today I lost an entire session of strip mining and some work on a church. This has happened to me the most (8-10 times over 2 weeks), probably because I am on the most. But almost everyone else on the realm has experienced it once before. We have all uninstalled and reinstalled our games multiple times now. Don't know of anything else to try