When you resize the ReactOS Application Manager window, then close it, then reopen it. The windows does not show up, and the CPU usage is 100% for rapps.exe
If you do the same with Firefox, it just throws a "crash report window".
You can get the same result by maximizing the windows and then close and re-open them. This does not happen when you restore the maximized window before you close it.
I did not test for regression.