Problems during homing, hits limit and keeps going


I have a problem trying to home the robot from Dobot Studio or Python code.

In either case the blue light blinks and the robot moves fully clockwise to the joint limit, then it moves very very slowly counter clockwise about half way around, then it speeds up, hits the other joint limit, and makes a horrible noise and shakes violently. I have to hit the reset button to make it stop.

The homing position is set to (250, 0, 0, 0) which should be reachable and in front of the robot. The documentation says it is Cartesian (x,y,z,r).