This bug has been bothering me ever since my last monitor crapped out and I was stuck with a smaller screen.
When maximized (with titlebar and taskbar) GZDoom ends up at the resolution 1440x847 on my screen, which is between 16:9 and 16:10. In fact, the resulting resolution is almost perfectly 17:10.
Anyway, I've been trying to fix this bug for a long time now, but to no avail. I can't seem to find the code where it actually draws the status bar. I'd be willing to implement a fix - if only I knew where the code was that calculated the actual status bar drawing.
(Oddly enough, at this resolution, executing "vid_aspect 5" produces no noticable change to the game view, but oddly fixes this...)