Just wondering if I am the only one with this issue, but since I upgraded to 7.8.2 , I got this error message when I modify must of my window under Window Manager, mostly all Knowledge Management Windows:
As a workaround, I can copy the window and modify the new window, but it's a pain to change all the window rule... Pretty sure it's a bug since the change they've done on knowledge management, all default windows are corrumpt.
If you have upgadred, give it a try. No need to do anything fancy, you can just resize one of your attribute, you'll get this error when saving.