FrontPanel Missing Panel Buttons


I have a FrontPanel XML file with 7 panels. When I load it in FrontPanel 5.01 on one machine, I see all 7 panel buttons. On another machine, I see only 6 of of the 7 panel buttons. When I use FrontPanel 4.5.5, the result is even worse, I usually see only 4 of the panel buttons.

Is this a bug? Is there a workaround? Is there a limit to the number of panels FrontPanel will support?