I am not sure about the wiggling. I do know people who have locked areas though. For myself I have very little range of motion. The people I know though with locked for ex can't open their hand. Has your neurologist or treating doctor seen this?
As for your pt does she/he work with people with neuropathy? I am not a fan of someone who gets upset or angry with you on this. This not your fault and their should be positive encouragement. I know I got yelled at in PT when I was at Cleveland Clinic but then it turned out the PT person was wrong in terms of what she was telling me to do.
I wish I had more to offer but hope things look up for you