QTR-Quadtone RIP

I've been successfully running QTR w/ gui for quite some time now, and
have recently discovered an anomaly in finished image size. I end up
losing anywhere from 1/16 to 1/4 of an inch from just one side of the
image. I'm running WinXP Pro, QTR w/ Gui 2.2.4, Epson 7600, UC inks w/
Eboni black, and Photorag Satin is the only paper that I think I've
seen this occur with (not that the paper has anything to do with it).
I think it's also happened exclusively with roll feed/cutter on, and
entirely on prints 16x20 and larger. I've since been printing from the
roll with sheet feed selected and so far so good with the first few
prints. 

Has anyone seen this? Any ideas? Bug in the Gui? Thanks in advance. 

Michael Gordon
www.mgordonphotography.com

Here's an update. I printed a 16x30 on Photorag original, same
settings as described in my intro post (but with sheet feed, manually
cut), and I got a 16" measured height on both short sides of the
print, but lost 1/32 on one 30" side, and lost 1/4" on the other 30"
side. This hardly even seems possible, but it's happening. When
mounting and matting, I can see the obvious sweep of the image
shortening. This is baffling me and pissing me off. 

Any ideas? Thank you. 

Michael Gordon