QTR-Quadtone RIP

I just installed QTRgui and the Piezography K7 ink set on my Epson 
2200, and am having problems with ink splotches. 

I am printing onto letter-size Hahnemuhle Photo Rag at 2880 resolution. 
I set QTRgui to use Matte paper and the correct Hahnemuhle curve. When 
the printer got near the end of the print job (about half an inch 
before the end of the sheet), it started to slow down appreciably, and 
I got large ink splotches across the entire margin of the paper.

I tried again: this time the paper shifted laterally near the end of 
the print job by about 1/8 inch, and I got a double image. It sounds as 
if the print heads are hitting the end of the paper, but only at the 
end of the print job. This has never happened with this printer -- at 
least not when using regular Epson color inks.

Any ideas about what might be going wrong?

Thanks!

- Chris Morgan