I'm not sure I can accurately describe what's happening to my screen here, but here is a screenshot:
Essentially, what is happening is that when I move my cursor to the edge of the screen, the main screen with windows moves in the opposite direction and reveals the GNOME carpet texture. The location of which the GNOME carpet texture appears seems to be arbitrary (sometimes it is on the left, sometimes it is on the right) though the location only changes through reboots. Occasionally, the GNOME carpet is replaced by a solid white.
I've tried to search Google for this issue but I could not find any search query that can shed some light on this problem (I tried: "debian desktop borders", "debian cursor edge desktop borders" and "gnome texture at desktop border").
I'm using an ASUS NVIDIA GT 710 (2GB) with NVIDIA's proprietary drivers. The screen I am directing output to has an underscan of 48px. Desktop manager is