I was just under mine the other day cleaning up some old wire mold at the step and I cut the sensor wire going to the step. I should have known it but it took me by surprise when the step closed ...right above my head. Good thing the fingers were out of the way.
Well, to get back on target...... with the circuit broke the step retracted. You sensor circuit must need ground to close - opposite of mine. But, you found the problem and fixed it. Good news.