Glad I could help!
Either the instantaneous change in stator field speed is getting ahead of the rotor due to its inertia and then failing to get back in sync, or you’ve hit the limit of what it can do with a 12V power supply. The specs in your previous post say ~220RPM at 20V, so 12V should be ~14rad/s. Perhaps 16 if you use SpaceVectorPWM which will allow motor.voltage_limit up to 7V.
In any case, open loop mode is really only good for testing to see if the hardware works at all. For reliable spinning and good torque, you’ll either need a position sensor, or once you get the current sense configured you can use the sensorless flux observer for velocity mode. It’s tedious to tune the parameters for it, but once you do it works well. But if your final goal is angle control, then you’ll definitely need a position sensor.
Try running the gimbal on the other side of the driver to make sure the Sunnysky hasn’t already burnt a mosfet. Sometimes they go out in a blaze of sparks and burnt fiberglass smell, but 17A is low enough that it would probably be ok for a while and then die quietly.