Game crashes when moving a player with frames, tested in a clean environment (only funky locomotion and thermal expansions to power to movers).
crash report
log

I got this same problem, and just to help you out here is the exact error
https://hastebin.com/ilopiyexiq.css
It appears net.minecraft.entity.Entity#isCollidedHorizontally doesn't exists.
I'm running forge version 14.23.3.2669 I'll update and see if that fixes stuff

Edit: nope still broken on forge version 14.23.3.2701

I think you're going in the opposite direction. The mod was compiled against Forge 14.23.0.2529, an earlier version. From looking at the sources on the more up-to-date versions of Forge, net.minecraft.entity.Entity#isCollidedHorizontally does not exist anymore, because it has been renamed to net.minecraft.entity.Entity#collidedHorizontally which would throw a NoSuchFieldError. If anyone is more skilled with Forge than I, it seems like it would be a pretty simple PR to throw together to fix it.