I had jittering and erratic operation on my 7955's too. I got rid of them. I see all kinds of guys reporting problems with the 7950's.
I really liked the 5955's and I used them almost exclusively for years, but they don't make the 5955's anymore. I have switched over to Futaba servos now. I still use JR servos on certain things too.
I still have some 5955's that I'm using, but I won't be buying anything else from Hitec. I just don't trust them anymore.

Jim