I have been on a realm with some friends for a bit more than a year now, and this issue has started happening repeatedly and consistently since the second week of April 2023. After any player or group of players is on the realm for anywhere from 10 minutes to nearly an hour, all players will be kicked with the message "Internal Exception: java.net.SocketException: Connection reset." The socket reset affecting everyone all at once leads me to believe that the issue is server side. 

Whenever this connection reset happens, progress reverts all the way back to the point of the first login since the last reset occurred. In short, progress is very difficult to make as all progress is lost after a connection reset forces everyone off. Given the timing, it may be possible that an issue occurs during attempted backups. 

These resets can be discouraging given the work that is often lost and the tedious nature of trying to regain process. I'd really appreciate a good look into the problem; thank you!!! Please don't hesitate to ask if more information is needed.

Edit 05/09/2023: I put this into a comment elsewhere, but feel it's critical to have here:

It seems to be dropping everyone on attempted automatic backup while playing – it tries to backup, appears to fail, and kicks everyone reverting progress to the time of initial login. The realm has gotten pretty large and the players have progressed quite far, so I'm tempted to believe it has to do with backing up a realm with large file sizes and a lot of active entities... These two characteristics are the commonplace from what I've seen looking around at tickets. 'Forcing' a backup by having all players log off seems to work just fine, not an ideal solution though. Also worth noting that I have not experienced this on other realms with less progress, big builds, farms, etc.

Edit 05/17/2023:

I downloaded the realm world into singleplayer; the realm's world folder is about 10GB. I am almost certain now that this is a folder size related issue.