Tl;dr: Random, frequent disconnects from the Realm as well as inability to access the Realm in spite of being able to access the marketplace. Not an internet connection/speed issue.

Initially I thought this was an internet issue, so I asked my other players if they were also being randomly, frequently disconnected. Yes, they are. I still reset my modem and router, reconnected, ran a speed test, and opened other apps of heavy bandwidth usage, and no other app is doing this. My players and I are in different states, and we use different internet service providers, and we all have ultimate high-speed internet suitable for streaming and gaming, so I have good reasons to believe this is not an internet issue.

Currently our online player count has maxed-out at five players. I pay for a +10 Realm, so that shouldn’t be the issue, either. I haven’t checked to see if this is happening on my +2 Realm yet, as that one is more for storing maps.

This issue started a few days before the most recent (as of 02/11/23) update, and persists.