Problem forcing GNOME Terminal to stretch across multiple monitors
This sounds like a bug and you should report the bug.
At first glance it looks like a design bug, something somewhere should allow you to make a window go over multiple monitors. Like F11 does for a single one.
But the second point is the corruption. Which looks very much like an error which should be fixed.
If both screens are the same size then you shouldn't have a problem but I can't really think of another way and I also have the same problem I just use Jupiter for only my big monitor.
sudo apt-get install jupiter