It may be a bad Hall Sensorclick on picture
The Hall Effect sensor is easily removed and replaced.
You’ll have to remove the rotor and stator to access the sensor.
When replacing the rotor, you’ll probably need a helper to hold the drum in place when you push the rotor onto the shaft.
Otherwise, the drum may move forward enough to make replacing the bolt difficult.
The helper can also hold the drum from turning while you tighten the bolt.
Before going to this trouble, check the connector on the main board.
It is the red connector closest to the heat sink.
Pull the connector off and verify the board is receiving a signal from the sensor.