Yeah, definitely get your mechanic to do the unloading part of the suspension and checking for play, and replace whats needed to be replaced. I reckon you could finally get this one cracked!!

Good luck, and thanks for the excellent updates. I say that because usually threads die when owners forget, can't be bothered to say what the fix was, or give up/put up, or just sell the motor, so nobody knows what the fix to the problem was!