Can't view intermediate layers

Hello, I am trying to view the contents of my intermediate layers. However, clicking on them has no effect, the layer selection indicator instead jumps back to my master layer and I cannot view the intermediate layer.

This happened after changing the values in the master, all intermediate layers and my virtual masters.

This is getting really annoying.
I can “fix” it by duplicating the glyph and then deleting the original.
When I reopen the file, however, it breaks again and I can’t click on an intermediate layer anymore.

I had that some versions ago but fixed it.

Can you explain that?

It has reappeared a lot even without changing the values, so that was not the reason. It is now simply happening when I open the file. It works again when I duplicate the glyph, but stop working again when I open the file again.

can you send me that file?