I have several 7700s DNs with only one feed tray. One by one they have all started jamming on legal-sized media. The first sheet starts to exit from the fuser into the receiving tray, and about 1/3 of the way out, the machine stops and gives a "jam at lower left" error. If I turn the machine off and restart, it works ok again until it runs out of paper. When I open the paper tray and reload, it jams again when it resumes printing. Turn it off and reboot it, and it works again. It seems like it is failing to detect that the media in the tray is legal, and is expecting letter-sized. I have 4 machines and 3 of them do this. Any one have an idea?