Tiling while printing is not retaining percentages

I recently bought an HP 6600 printer to replace a cheapo Lexmark printer.

I'm making maps -> photoshop to Illy to print with tiling set at 6-8 pages. When I print on the new HP, the resize percentages are off; so streets, numbers, text, etc. do not line up when pieced together.

This did not happen with the cheapo Lexmark, so I am assuming that it is the printer?

Any ideas on what is causing this and how to fix it?

TIA