I’m not exactly sure what’s causing it, but my game randomly freezes. I can still hear other players through voice chat and hear blocks breaking, but the screen becomes completely frozen. After a few moments, Windows shows an error like 'This app is not responding,' and I have to force close the game. When I restart and try to unvanish using /vanish, it crashes again immediately.

latest.log

Hello, unfortunately the log doesn't really hint at a concrete issue within Vanishmod. I noticed that you have a lot of other mods installed, so a mod incompatibility is likely, however that's not really possible for me to figure out, especially for stalls (or out of memory issues?) like these.
What you could do is a binary search: Try if vanishmod alongside half of your modpack causes this issue. If yes, try half of the selected mods. If not, try the other half of your mods. That way we could at least narrow down which mods might be involved (it could also be an interaction between 3+ mods, which is always fun to figure out).
If I'm not hearing back from you in a month or so, I'll close this issue, since there's nothing that I can really do to address this without further info. Feel free to reopen it tho if you have some new information.