There should be a red cord hanging down. Turn of the power if you can see the switch (not really necessary). The door should move freely if the cord is pulled down. Slowly close and open door very slowly, looking in the corners to see or feel any resistance. If you see or feel any rubbing/ resistance, try and adjust that area. Sometimes backing of the bolts in the wall/brackets or even bending it by hand can help.
This is what happens when kids swing on the tracks or hold on to the door when it gets opened, lifting them up off the ground.