can you show us what the ragged edge looks like?
Couple ideas:
You've maybe set the print size a tiny bit longer than the printable area, so the printer runs out of paper before it can finish the job. QImage is a bit quirky sometimes so I've found it's easy to get sizes slightly wrong, especially when borders are involved. Are you using borders? Are they set inside or outside print area? An inadvertent shift from inside to outside would make for a slightly longer print.
The printer is loading the paper a bit to far in before starting to print, causing the image to be placed further down the page than normal. printer runs out of paper before image is complete. No idea how one would correct for this.
The edge is not actually ragged. What is happening is that the last couple of lines of the image don't get printed over, or printed fully, so that sections of the last 16th of an inch or so are lighter, with less detail.
I'm not using borders. I had been sending files from the 1DII and now the 5DIII to Qimage, to "Fit To The Page."
The printer driver is set to Center Image and Max Print Area. Qimage is set to Center placement. The page size, as sent to Qimage from the Printer Driver was 10.766x8.26, and it was the trailing edge on the long side that developed the problem.
The printer is loading the paper correctly and starting the print exactly where it has for a year when printing on 8.5x11 paper.
What I did today was reduce the page dimensions in Qimage to 10.69" on the longer side and the prints are working fine again. They are .08" shorter on the long side, which is fine for my purposes. I am still curious as to why the printer had been OK for a year or so, but it is possible that something in Qimage got changed somehow.