Seems there is a little glitch somewhere in the geodsic...
As soon as the up Knob is decreased/ increased there is new a sphere who is drawn inside
and that calculate for a moment...etc ...and that blocks all things! ;)

And i believe it's more prudent to put Curseurs because Knobs are very sensible to the direction of rotation
with the mouse so increase can be not wished and too late for take back in the case above!