Ever since I started playing 1.17 whenever I join my Realm I have about 10 minutes of playtime befor said error occures and the conncetion ends. Attempting to reconnect is meat with the error immediatly. Restarting my PC only gives me another 10 min until the next dissconnect.

Also there seems to be mutiple people having this issue on reddit, without a solution so far:
https://www.reddit.com/r/Minecraft/comments/nvdcxj/117_connection_reset_issues/

There also is an issue on this forum that has been shut down without answer:

MC-228511

If you consider this a technical issue I urge you to convert this ticket to the proper form instead of closing it.