Hair shifting on head

[GlacierFrostclaw]

So, my mod has a certain issue that I can't figure out anymore. Basically I import manes and tails from Gmod and SFM pony models into Fallout 4 (with permission from the original models' creators, of course) for an addon for Crimes Against Nature. I seem to have forgotten a key step in getting the manes to work, though, because for some reason any mane I try to import now will slide to the left or right of the head depending on the direction that the character is looking. I've made a video showing my method as well as the issue in-game. I've tested the old manes and they still work normally, so it's not an issue with the other mods I have installed. If possible, could someone help me out? I'd really like to get back to working on my mod.