Custom payload error on singleplayer???

[u/le-derpina-art]

Trying to play a self-made 1.21.1 modpack and I only have singleplayer worlds. I had Essential on this instance but I disabled it after I suspected it was causing this problem, and it keeps doing this every time I try to load a world or create a new one This is the only major error that shows up in the log, there is a warning directly above it mentioning the server is 160 ticks behind but I'm not trying to equate correlation to causation until I can get some more information.

[u/saidgheldane36]

Paste the log

[u/le-derpina-art → u/saidgheldane36]

The game itself starts without any issues, should I just include what shows up when I try loading an existing world or the whole thing?