hub motor weird inner gear problem question

[robert21]

Hello, before opening my rear hub motor which is a part of the wheel,i wanted to ask your help with advice.
last time i open the motor i saw three outer gears co-rotating.

when i ride my bike,when i stop pedaling and the motor needs to stop working, i hear very hard gear grinding.
when i start pedaling again, the gear makes noise but start working no problem.

The most intresting happens when the motor stops working i just lift the back wheel hit it a little against the ground and the gears are fine working again.
What could cause cause this issue?
Thanks.

 

[MT Krooner]

You can open up the wheel hub and see if you can find what is making the grinding sound. this video will give you a visual of what's inside the hub that could be making the noise:

here is another one: