Krups 239 Power X Plus Work Top Blender stuck

The motor works, but can't rotate the blade when the unit is empty (or full). I took it apart and it seems that tightening down the jar restricts the movement of the blade so that it cannot be rotated.

I've tried not tightening the jar all the way down, and the machine works in an unsatisfying manner. The blade jumps about due to the extra vertical space and the jar feels wobbly when I move it.

Is there a way to tighten the jar to it base without pinching the rotation base for the blade?