No Stop button in window
The big defect in OS/2 that I met was the lack of a stop button in any window. Yes, you could close the window but that did not stop the task, just left it sitting in the background.
It was Windows 95 that brought us a proper stop button.
We had an OS/2 system returned to us as not working. The user had been closing the window, and then later starting up another instance. The system was clogged with dormant tasks. Once I removed them, everything worked again; what we had to do then was to update our User Guide.
Biting the hand that feeds IT
