J50C

Hello. I have a 1.17.1 server, and I switched it to 1.16.5 so I could use replaymod, but it would throw an error and send me to the minehut lobby when I tried to join it. I thought this had something to do with the connection issues of yesterday, but after a day of checking and finding nothing changed, I tried switching it back to 1.17 and it worked. We presumably only worked in previously loaded chunks for the time we were in 1.17. Is this a known issue, or is this just how minecraft works, because I'd like to have replaymod access for the build I'm about to, well, build. Thanks in advance.