My browser / operating system: Windows NT 10.0, Chrome 138.0.0.0, Flash 32.0 (release 0)
if you switch the rays backdrop to bitmap then back to vector it crashes the editor

In the project linked in this thread tested and the costume editor crashes.

My browser / operating system: MacOS Macintosh X 10.15.7, Chrome 139.0.0.0, No Flash version detected

and Safari 18.4 (18621.1.15.111.1, 18621)