So I've been troubleshooting this for a while and can't find a fix.
When I try to close applications by clicking the (x) the window maximizes instead. The issue only seems to apply to applications with custom designed buttons e.g. Steam, Discord, Origin, and such. Works fine with browser and built in programs.
It doesn't do this every time, sometimes it just works, and sometimes I have to click it a few times (maximizing and "normalizing" it) until it eventually closes.
I've disabled all DisplayFusion title bar buttons and tried to disable and enable everything that I can find in the settings that sound remotely relevant.

Have you heard of this issue before?

Attaching the debug log. Got a few good issue samples at ~20:43. Used Origin to reproduce the error if that matters.

Thank you for your response!

That's great news! Thank you very much for your time and support!

Another data point: I am having the same problem.

happenning to me with epic game launcher
i'm on a single screen split in 3. steam version

here you go

after testing seem to append only if i click in the middle of the button.
left, right and up does close. (up is narrow)
if restore it maximize and if maximize it restore

this should be automatic for steam install?

ok update to 9.6.1 and it ok at first look