The mod works fine until you unvanish. For some reason after exiting vanishing people see me in places I'm not actually at, this is because I move super fast on their screen. For example, on my screen I walked 5 block forward, while on my friends screen I basically teleported 50 blocks forward.

On top of this, when I die I am permanently completely invisible and can't move anymore. Leaving and rejoining seems to fix the issue entirely but it's still weird.

Hello, that's a weird sort of issue... What versions of Minecraft and Vanishmod are you using? And are you using other mods alongside Vanishmod?

Same here, i am using Vanishmod-1.20.1-1.1.18, with a 200+mods modpack.
This modpack:
https://www.curseforge.com/minecraft/modpacks/aetheros-smp-modpack-oficial

And the version of minecraft is Forge 1.20.1 - 47.4.0

Ok thanks, that's a lot of mods you're playing with, so my guess is that this is some sort of mod incompatibility, which are always hard to pin down. If you'd like, you can do a binary search with your 200 mods (removing half of those mods, seeing whether the issue still occurs with Vanishmod, if yes remove half again) so we can narrow down a bit further which mod might be at fault here.