vivivivivibration

The lack of a motor mount really.....BTW, OP, if that is a cheap Indian or Chinese made mount, don't count on it lasting. Their rubber varies from questionable to hardened cow dung. IMHO that is real issue with broken mounts....

Try to find an NOS ones for motor and trans, or from a better quality mfr like Schumacher.

Glad you made progress and thanks for reporting back; it will help others.