Please take a look at this article for documents printing from the wrong tray.
If you are still having issues after trying these steps please call into the support department at 1-800-835-6100.
I have a WorkCentre 6515 printer. I cannot print from my computer. I want to use tray 1 but by default, tray 2 is displayed with the manual start and I cannot change it. Do you have a solution?