thank you for such prompt reply Chong,
I know it kinda looks that way, but the problem is that the bones are weighted and the proper regions are assigned to them.
you can see on the screenshot (on the right) that bones are actually moving/affecting assigned parts of the arm. the unusual thing is that this happens with sorth of a 'delay'.
each assigned part moves 'slower' than it's bone, resulting in dis/placement of the bone way outside of the assigned region in order to achieve the desired position of the region.
(in this particular case bones were manualy weighted, with every bone affecting 100% of it's assigned region).
you can check out this screen recording for a better representation:
https://we.tl/t-oEQxpJg8zz
thanks again!