So I've had this weird bug for the longest time, and I seem to be the only person with this problem. I assume because I've seen no other topics about it or people asking about it anywhere.
Enough rambling and onto the problem. Tassets and kilts seem to be bugged for me? Whenever I run diagonally in different directions the tassets/kilt for light and heavy armor likes to freak out. Running NW causes them to stretch out to the NW and SE, but if I run to the NE it doesn't do a thing. Sorry for bothering all of you, but if anyone has any solutions they'd be greatly appreciated.

It does that for ALL the armors? And how far/big is the stretching? Does it go on forever or it's just small stretching but looking bad? It's hard to explain without visual reference.

Do you have any mods that modify the vanilla armor meshes? Look in Data/Meshes/Armor. If you have this folder. But it can always be a packed file anyway...
Minor stretching (or serious, but not the type that looks like an artifact) could mean improperly skinned meshes.