Closed [stable] Perplexing issue, extreme input lag on new characters

For some very strange reason, brand new characters I make have this sort of extreme input lag on them (typing text into chat takes a long time to show up, saving takes an extremely long time). This issue just started right now. I have two others characters I made yesterday, they work perfectly fine (when I save and quit, its back to the menu in like 2 seconds, chat shows up instantly); no issues at all.

I haven't changed anything in my game at all before this issue suddenly showed up, and its affecting every new character I make, while the characters I made yesterday function completely fine. I am using the S3r1ous Mods modpack, but started a fresh universe and fresh characters after putting it in, and had absolutely no issues from yesterday until just now.

Any ideas what could be causing this?