Broken when not in full screen (Windows)

[ReimarPB]

Using this CSS makes the browser completely broken for me:

I can resize the window, but I can't move it by dragging the cursor on the empty area at the top. To move it, I have to press alt + space and click 'move'. This is the case no matter how I resize it, except for when the browser is in full screen (not maximized, I have to press F11):

I know I'm using Librewolf here, but I tested it in regular Firefox as well and got the same results. Specifically, I have tested it on Librewolf 99.0.1-2 and Firefox Developer Edition 101.0b6 I'm using Windows 10 version 19043.1706

[TRPB]

I'll have to try in a Windows VM as I'm on Linux but I'm surprised it's that different, if you remove the bookmarks bar is the layout still broken?

The move thing is interesting, this CSS doesn't change any browser events it just moves stuff around. I wouldn't expect it to be draggable via the address bar but the tab bar should function as it did previously.

[ReimarPB]

Yeah, it's the same if I hide the bookmarks toolbar.

I actually found out I can move the window if I am dragging on the white part (the empty space next to the address bar), but the dark part to the right (which I have otherwise used to move it before) no longer works.