I don't think it is a mechanical problem at all.

The thing that is different when duplexing is there has to be a delay (compared to non-duplex printing) in picking up the next sheet of paper while the back side of the page currently being processed is printed. This delay has to be coordinated between the pick roller and the feed/registration roller.

It appears that either the pick roller is not waiting through the delay period and sending the paper to the feed/registration roller before it is ready for it, or else the feed/registration roller is not getting the signal to take the page from the pick roller.

Because Tray 1 and Tray 2 both use the same feed/registration roller, and Tray 1 duplexes properly while Tray 2 doesn't, I would suspect the problem lies with the Tray 2 pick roller sending the paper to the feed/registration roller too soon.

This suggests a logic failure, perhaps a corrupted driver or firmware. It is a long shot, but I will download and reinstall the printer driver and see what happens. I'm not optimistic that it will solve the problem.

tanstaafl.