Created attachment 869042 [details]
Result of "Export" window rules

I have a 4K screen so that I can tile several windows and see their contents all at once. To get six windows on my screen I force the sizes of all windows to be 1280 by 1058 with exceptions for a few applications like konsole which need special shapes. I've attached a dump of my window rules.

System Settings opens a window which is larger (1530 by 1091 with no force DPI and Global scale at 100%). If I modify and reapply the rule, the size of the window changes to 1280 by 1058, and subsequent windows opened by that invocation of System Settings get that size.

If I quit System Settings and start it again, it sometimes opens a window 1280 by 1058 and sometimes opens a window 1530 by 1091 again. I haven't yet discovered any consistent behaviour. After a reboot it always opens a window 1530 by 1091.

It doesn't seem to be possible to attach two files to a bug report :-( , so I'll attach a hwinfo in a comment.