I used PowerToys' FancyZones on my secondary monitor, and when I use StartAllBack, the taskbar ends up over the window in the FancyZones', well, zone.
I expected to see the bottom of the window, like this
I don't know if this is a bug in StartAllBack or in FancyZones, but I figured I'd report the bug here first.
When editing the FancyZones, it looks like they would stop on the upper edge of the taskbar, but when I actually assign a window to the zone, it is larger, so the bottom of my window ends up hidden behind the taskbar.