Left arm moving during custom animation?

I am trying to get my left arm to stop moving while walking during the idle animation. Here is a video of my problem

I have tried changing the animation priority, I know that the animation is looped, and I have tried welding my hand to the weapon. Does anyone know how to fix this? Thank you.

I believe this is an animation issue. Check if your left lower arm has a keyframe in the animation you made. If it doesn’t, the run cycle probably overlapped that and plays the run animation on the left lower arm instead.

It’s definitely the latter problem, but I don’t know how to fix that issue.

I figured out my problem by myself.

What was it? I am having this same problem