Printer printing off

[capitate]

I have a Roland RF640 and for some reason it is finding width sizes like 54.5" or even 55", and it also isn't printing center, even printing over the edge

Anyone seen this before, and can give me some clues as to what might be happening?

 

[victor bogdanov]

Dirty Encoder strip probobly

 

[cornholio]

The paper sensor or the reflective strip on the print platen might be dirty.