I think there's a piece on Rebel Scum, that explains how some people claim there was a short FX-7 variation, but in actual fact it's just the figure with the bottom missing. Just checked, here's the link.
http://www.rebelscum.com/VINtFX7.asp
With the bottom piece simply been glued on, it's probably fare to say it's a production error in the sense it's been glued wrong.