how do I unstick a retracted Main Oven control knob of the Neff U1541 ? ?

The knobs do not respond to attempts to rotate them very slightly (thinking a lug may have jumped out of its groove) but appear to have locked in at the end inside. I have removed the several Torx screws which appear to hold the Knob unit in place (this appears to be the way to get at the innards) including a screw at the side, but the unit shows no sign of wanting to budge - and am reluctant to lever it. So what do I do now ?