"the "bobbin race hook assembly unit" does not have any motion even within itself, whether on or off the machine. This seems wrong."
That is your problem... You will have to take it apart and put it back together again. ARGH. It can be a wee bit of dust, rust, burr, thread, dried oil, or assembled slightly wrong, or assembled right but nestled wrong - let us all know if you find anything
somebody pass the popcorn