Four corner motion track not tracking/wandering corners. Help needed.

The tracker probably isn't broken — it's always been that way. Anything that can cause it to lose "focus" on a tracking point and it will lose its place. [BTW — I don't know what the icon means.] Each tracker really needs a definitive point of contrast to track.

You can't track anything that goes outside the project/canvas bounds — the tracker will automatically just stop. So if you have something like 4k in a standard HD project and what you're tracking goes out of bounds... it just won't work. You have to resize the original media to fit.

As long as you have at least one point tracking properly, let the Analyzer finish, then turn off the point in the tracker and try to repair the others. This tutorial might help:

https://youtu.be/qZk0UqX6HP8

In the 17 years I've been using Motion, aside from initially trying it out and a tutorial or two, I've only ever used the four-corner tracker when trying to diagnose issues like this.

I've always been faster handling it manually than the tracker (unless the footage was *perfect* for tracking — which is rare.) I know that manually tracking is mind-numbingly tedious, but I know I save a ton of time not having to deal with the automatic tracker. [Point of fact — still using a 2017 iMac i5... YMMV.]