Corner components on extra nodes

Corner components on crossing paths are very useful. But sometimes they don’t work and I can’t figure out why. You can see it in this example, there is this square block instead of the corner component.
When I move the nodes I can find positions where they show up again (image 2) but it’s very random.

Also, some letters that worked fine a few versions earlier now have this problem. I am now on 3.0.2 (3042).
I tried to open a backup .glyphs file that was working last wednesday. Today I can’t export it because this problem leads to incompatibility between masters.

I’m working on the corners on intersections.
And can you send me that file?

Sure. Thank you!