Document feeder down only copy mode on 6180MFP

Hello everybody,
I have an Xerox 6180MFP and I have a problem with the document feeder but only in copy mode !
When I charge sheets on the document feeder, in copy mode, the scanner uses the glass nevertheless... The switch isactuated.

Also, when I'm in fax mode, the machine scan the papers in the document feeder.


I have bought this printer recently and I install this at my home. When I bought it, I seem to have tried to copy with the document feeder and I had not had any problems. Since I did the firmware update with the last one on Xerox website, is that it could come from it?

The problem can't be physical, I think !

Could you help me please ?
Thanks !
Aurélien, France