Bug: Can't delete Element from Page

Frame0 Version: 1.0.0
macOS: 15.6 (24G84)

I can’t remove the rectangle from the Window element anymore (while it sits on top of the Window element). If I move the rectangle outside of the Window Element, I can successfully delete it.

The rectangle has a reduced transparency in the Layers view but I don’t know what that means and I can’t change anything about that.

I sadly don’t remember how I got the page into this state.
See attachment for minimal example to reproduce the bug.