the title says it all execpt for its on 1.12.2

Please show the vehicle in question, with the F3+B bounding boxes shown. I've seen players fall through in 1.16.5, but not 1.12.2. Perhaps the main bounding box isn't encompassing the other boxes enough?

oh shoot, I forgot I made this issue, I am going to do that I was booting up the game anyways

The berlin plane I showed worked mostly fine, but the generic one and the blip clearly had issues
https://streamable.com/ji3eue
it expires in 2 days, ill upload it again if i remember

This looks like you have a mod or something conflicting with the player's collision and bypassing the normal code and enhancements that IV uses. Try removing mods until you find the one that is causing this. Alternately, you can join the Discord and we can chat there and go over things, but since I and others can stand on vehicles, this must be a confict with your specific modset.

well unu vehicles work fine and collision with regular iv vehicles is fine just the big ones don't work fully and mainly near the driver/pilot seat

Again, if you want this fixed, please follow my instructions. You're the only one who has this issue, and unless we can find out why, it won't get fixed.