I am wondering if the problems that you are experiencing are related to something happening with the torsion spring inside Axis 2 (the Shoulder) becoming unseated from it’s mount in the Arm Bottom.
I was surprised at the strength of the torsion spring during the assembly of the v2.0 robot. It may have to do with the differences in the assembly procedure compared to v1.x, but I am wondering if I the torsion spring in the v1.x robot that I have is having some issues. Neither of the robots that I have is behaving as extremely as what @wodcleaner shows in his video; I really do suspect that what he is seeing is a fully unseated torsion spring.
It would probably be best to see what Edouard and others from Niryo might advise, but it might be worthwhile for you to disassemble the Shoulder to check whether the torsion spring is still seated properly.
I have had some experience disassembling the Shoulder. It is somewhat difficult to accomplish. You need to use a regular screwdriver and a putty knife to carefully coax the torsion spring out of it’s sockets in order to get the Arm out of the Shoulder.