Window jumps around when dragging across 4 monitor setup (2x2) when panels are placed on the bottom of the top 2 monitors

I have 4 monitors, 2 on top of 2. I have a separate panel on each monitor (each placed on the bottom). As I drag a window from one of the bottom monitors to another one of the bottom monitors, the window jumps up so that the title bar sits above the panels on the top monitors. When I remove the panels from the bottom of the top 2 monitors, then the bug goes away.xfce_xfwm_bug_small