I can relate to the arm problem, similar experience about 92 right arm shoulder to finger tips, Never got a specific reason but stoke was in the list, docs and pt people said about a 40% recovery would be max- not an acceptable solution. took me about 3 years to get back 98%, although not permanent according to docs, but its 2014 and still have better than 95% - got other parts that have faired worse over the years though.
my problem seems like a muscle problem & I assume the muscle is contracting, which causes my arm to lock up & puts me in alot of pain. & thanks everyone, I figured I would get slammed for asking about the junk saw, but its out of necessity, not because I dont know better, or just wanted to waste money modifying something thats basically a throw away saw.