I have 4 masters Thin/Reg/Bold/Black
I added a Semibold instance as a new in-between master.
I removed the Reg Master
The in-between instances got wiped. See image below
I then selected the in-between instance to remove them and Glyphs 3 crashed. (i selected them and hit the - button bottom right)
With “got wiped” you mean the icon disappeared? That might be because the renaming masters are not compatible? Or the interpolation got confused. So you might need to save, close and re-open the file.
Edit: I fixed the missing update of the icon. Thanks for finding this.
They seemed to have no content. I was basically going from 4 masters to 3. In the past, the interpolations seemed to refresh automatically when adjusting the masters but this time something went wrong. I though it could have been a brace layer but that didn’t seems to effect it.
In the end I simply removed the old instances and manually created new ones.
Might be worth looking into.
As I said, I fixed the instance problem already.