Grounding the case only tests the wiring between coil and driver board & doesn't test Q45.
Make sure wiring between Q45 emitter and ground is OK. Original connectors/contacts?
Are you sure the U45's are bad? Could be the corresponding 2N3055 at Q45 - might have lower than normal gain.
Where did you get the 2N3055's? Not Toshiba's by chance?
Not likely but also check resistor R39 for proper value and not shorted.