I had a strange behaviour of my Ultimaker 2 extended yesterday : the filament was going backward !
The feeder was confusing up and down, back and forth. Impossible to move filament except with the advanced settings.
The answer was given to me by Sander : I did a wrong firmware update, using the UM2+Ext firmware instead of the UM2 Ext.
So, for those like me that a dumb enough to download the wrong driver and before your take a screwdriver to unmounted the feeder, or before crying on the shoulder of the support : check the firmware !!!
John Doe (so ashamed!)
NB : thanks for Sander vG. who did promptly solve my problem. Not only this company makes excellent products but they also deliver great services. Who wants more ?