Sounds like you could have either an improperly tensioned or damaged drive belt between the motor and separator bowel drive shaft, damaged/worn belt pulleys or a fault in the settings or function of the VF Drive speed control for the drive motor.
Worn or damaged bearings in the motor or on the bowel drive shaft can also put drag on the drive causing the bowel to slow down
I can't remember the configuration of the belt drive but if the belt tension is not correct or the pulleys are worn out or damaged the bowel will be slow to spin up to speed and slow down when product is admitted to the bowel.
If there is any kind of oil leakage from the separator on to the belt will also cause the separator belt to slip.
If there is a fault in the electronics or bowel speed feedback sensors of the drive motor control could cause the separator to fail to start and give the P180 fault alarm.
Troubleshooting 101 "Don't over think it - K.I.S.S. it"