Did this ever get resolved? It is still happening to me..
Have you tried turning it on and off again?
I seemed to get this to work by printing by paper type instead of selecting the tray itself. From previous experience we've been able to just select the tray and that printed the whole job without problem. Not sure what changed but paper type as labels and setting that for tray 5 as well seemed to resolve the problem for now.
We have a Microsoft word document that we're trying to print to labels on the bypass tray with the lables loaded. When the job is sent it'll pull the lable paper correctly for 2 or three pages and then it stops pulling it and instead switches the job to another tray and prints on normal 8.5x11 paper.
Usually the problem i've had is that it won't print from the right tray but once we get it to it does the full job correctly. I'm not sure why it's switching trays halfway through, any ideas?