Extended monitors, dropping windows

At work we are using dual monitors on our Mac workstations to post-produce video products. However, our extended monitors are dropping part of the windows when we attempt to stretch the view across both monitors. Whatever portion of the window that is stretched over the secondary monitor continues to be dropped, no longer visible. I've already "fixed" this discrepancy on one of our workstations, however, I cannot recall what steps I took and failed to take notes.

How do I extend the desktop over extended monitors without the secondary monitor dropping the image?