I came across a very annoying problem this night. I have modeled a jacket for M4, grouped it and already made it to a conforming cloth. Most parts of it pose fine along with the model, only the sleeves give me headache because they are kind of "glued" to a spot and will only distort and split instead of moving. I first thought, that I could have missed some parts while grouping but from what I have checked so far, everything looks right there. I attach an image and would be really grateful for any help. (ignore the general pokethrough on the hand, will fix that later)