Is it definately A.C driving the motor?
Sorry, i can't see whee the voltages come from, beyond that 4-pin connector on the left side of schematic....
To me, it looks like a typical DC driven motor-switching arrangement, the electro's probably used for de-glitching the relay contacts during changeover etc...
You might find 1 cap is open, or even low impedance causing your 'shuddering' problem.
Anyway, changing the caps is a good start, easier than finding that motor :-)
A modern .01uf 630v greencap will be fine.
MM.
