Ok well it might be related.. I attached in this case just my TV to my minidp->hdmi and it in this instance only failed to draw a small portion to the far right on my laptop screen, and the first image shows when I minimized my terminal, the 2nd shows me trying to drop an icon there, the 3rd shows after I've changed the background image.
The icon thing in this scenario however might not be relevant cause in the last screenshot I am showing one of the screenshot icons being as far right as it'll let me place it even after the issue is resolved due to a bg change, and its still not letting me put it in that area.. I will try generate a situation where it has a larger area.. before it was routinely doing about 1/3 across the bottom of my 1080p laptop screen with the configuration I was using which is a larger test area..
in this screenshot I have 3 displays configured with a much larger area affected and the screenshot icon shown is as low as it'll let me drop it
and in this last screenshot, I've refreshed the desktop bg and moved that appearance preferences all around the affected area, and as you can see its no longer failing to redraw that area as its not showing the appearance prefs window all over the screen, but it still will not let me drop that screenshot icon any lower and as you can see the filename is only partially showing where it is right now.
so idk.. I can perhaps try more testing if someone could come up with more ideas I tried an strace, it generated about 5mb in a short time and seemed mostly useless. I think I'd need a special dbg version of caja to use gdb, idk I've never used those things before but I'm more than happy to help run this down further if I can get some guidance on how to do it.