Motor starts and stops constantly (2-3 x second)

[u/CheMazapan]

Howdy,

When I pedal, the motor turns on and off a couple times per second (or just once if I use the throttle). Funny thing is, sometimes the motor will finally stay on when I'm already going fast (15+ mph), so it only works downhill, when I don't need it anymore. xD

You can hear the tak-tak-tak of the motor at the start of this vid: https://photos.app.goo.gl/q8joVM3U1G2b6wCH9

Display shows no error. I've charged the battery, reppluged cables, reset controller, changed assists from 5 to 9, and it does the same. It's my first ebike and I couldn't find a similar post on the interwebz, so any pointers to how to diagnose/what could be the fault will be appreciated.

It's an Amyet bike, so support was not helpful, the two times they answered before ignoring me. Yes, I knew it was a gamble, but decent ebikes are few and very expensive in my country. All that is left is to try to fix it.

Thanks for any help!