Hey there! I removed Bobby as Pyralis suggested and found that I still had that and a another closely related bug (or same bug, different presentation) wherein a torch only illuminates its own block and gets smoothed 1 block out, then gone.
After comparing your modlist to mine (I'm on fabric, also 1.20.1) I found we had 2 mods with the same versions.
Mine || Yours
Bobby-5.0.1.jar ||bobby-1.20.1_v5.0.1.jar
ImmediatelyFast-Fabric-1.2.17+1.20.4.jar || ImmediatelyFast-Forge-1.2.17+1.20.4.jar
Removing ImmediatelyFast.. immediately (๐) seems to have fixed the issue. Since it's client only- no new world needed either!
To note, I also removed all mods related to or containing direct requirements for Sodium, Indium and Iris which may have played a role, I did not test with re-adding.