The watchdog trip was a comms failure between the upper and lower boards, this was usually down to EMC, electrical interference. I may be that the motor is not Bonded correctly to the inverter earth plane. Check the motor cable which must be screened and bonded at each end, with no interuptions of the screen by isolators.
Also try turning the switching frequency low, P076, make it value 6 which will be 2 kHz. If this works, by reducing the EMC generated by the inverter, then this confirms the bonding for the external circuit is poor.