When preparing to throw a spear, the animation will leave the top layer of the skin alone while the right arm is raised.

Unfortunately, I don't know if I can solve this issue. The way I use to change position of player's arm is very clunky and I haven't found any better way to do it.

Quark found a way to do it with its emote system. It might be because of AutoRegLib, however.

Quark is actually a coremod and therefore it can add features, which are impossible otherwise. I want to avoid coremodding because it can cause a lot of problems when not done properly and I am not that good at Java. And with no other way to fix it, I decided to remove the arm rising entirely. :(