The "forgotten post" does happen. I've had two get skipped, then suddenly explode about two weeks later 
Timing is everything.
The chassis ground and full bridge not working was what I hoped you understood. It's one thing to swap parts, another to know why.
What (still) has me confused is why it needs rectification at all if it is an open frame ac brush motor. Direction change using two diodes is all I could think of. I couldn't find an online reference to it at all and haven't ran one since I was about 8, many decades ago, but I don't recall it being bump and go either.
Does it have magnets in the motor?
