"Just sitting" on the machine should never cause it to bottom out. If it does, your torsion springs are likely pretty well sacked out and/or are not in a high enough setting to support your weight.
Additionally, there could be issues with the skid that are causing it to collapse when it should not. With the skis and the track on a flat, level surface, check to be sure that the skid rails/track is in contact with the ground over its entire length. If it is not, I will predict that the FRONT of your skid is touching and the rear is not.
If you have good contact over the entire length of the skid, on both sides, then definitely look at the torsion springs as the primary culprit.