9-Slice Scaling not working on illustrator for windows.
9-Slice Scaling is not working for me and I don't know why. I've seen multiple youtube videos showing it working in action (in illustrator) but for some reason my setup isn't working.
This is the setup I have with the guides on the image (it's hard to see), they're just outside of each of the corners so the sides will stretch but the corners will stay the same.

This is what happens when I squash the symbol. Instead of the vertical edges retaining their width, they've become really skinny, which as far as I understand it, is not what 9-Slice Scaling is supposed to do.

The only thing I can think of is that I'm working on a Windows PC and not a Mac like the videos.
Videos of 9-Slice Scaling working:
https://helpx.adobe.com/illustrator/atv/cs5-tutorials/using-9slice-scaling-options-with-symbols.html
https://www.youtube.com/watch?v=dk3XIaAX7eA
The Symbol is Static (although I've tried with Dynamic) and set to Movie Clip (I didn't bother testing Graphic because apparently those values are only for flash). I'm using illustrator version 24.0.2 but I also tried in 23.1 and 23.0.2.
Any and all help is appreciated!
