I have just picked up this machine for a bargain and it prints / copies etc perfectly well EXCEPT after it has switched into eco mode for any length of time.
The first attempt at a print job will ALWAYS result in a jam but there is no paper jammed! If i go through the motions of clearing the jam, eg open front door, duplex unit, side door and paper tray - rotate the blue paper feed knob and close it back up it will print fine until it shuts down again.
The jam is in the paper feed path just after picking the paper up from the tray, according to the machine its jam 'B'
One thing I have noticed is that the blue paper feed knob is tight to turn for 1-2 turns and then loosens up every time this occurs and I am not sure if the machine is seeing this tightness as a sign of a paper jam.
I tried printing for tray 2 and it printed perfectly with no jam of any type so what ever it is it must be related to tray 1. I might just leave it unless some one can think of a reason why it might be doing this!