So i just got the Perk for beheading people, but as i tried to decapitate a guard, the animation played, but the guards head stayed on the body. or at least the helmet did, because as soon as I looted the Guard and by accident took his helmet, i could see the neck with the wound and the head nearby on the ground, seperately. when i looked closer the next time i beheaded a guard, i saw that the moment i cut his head off, and the head should actually be flying away, i can just see the texture of the cutoff neck, that is attached to the head, fly away. the head appears as soon as i take the guards helmet. This only happens to the regular guards, e.g. whiterun.
Help would be greatly appreciated

EDIT:
here are some screenshots:
http://cloud.steampowered.com/ugc/594705620016128140/DA10F3F3E0AD73959EDE2491E48EFC46FAC41511/
before taking the equipped helmet

http://cloud.steampowered.com/ugc/594705620016134370/E05EDFFE2BFEE6B1EAE4994FF2DF4FF057825437/
after taking the helmet of her inventory

please, help anybody?

Yeah, if you take helmets off decapitated heads, it seems the mesh doesn't get updated properly. You get transparent areas or bits appearing/disappearing when they shouldn't.

yeah but the funny thing is that it usually works perfect, i even beheaded an alik'r warrior once and there was no problem, even though they have these special hoods.
but thanks anyway, it's relieving to know this isn't my problem only, but common.