Neck, t spine, and shoulder restrictions can impact the trap and its ability to perform.
Your left side may compensate for the right side if there are restrictions or something that you may not have been aware was happening.
Yes resolving the restrictions at the neck, t spine, and shoulder can impact your traps ability to perform.
No I don’t think it sounds like something that can not be improved with the correct attention. I have had nerve regeneration in my quad and proper function is returning as it is addressed. It can take time which mine has, but it is improving.