Can't get tracking stabilization to work - v3.6

I’m trying to stabilize a video, and am following this video:

But I get halfway through, adding autoscale… and then it all falls apart. There are no tracking marks to indicate that the tracking worked, and even more, on the 2nd frame, the screen goes to a single colour that wildly fluctuates in hue. Maybe blowing up 1 pixel to the size of the screen?

Any suggestions?