You have the old style steps with only a single bar joining the steps. These tended to sag in the middle and were springier to climb. Look closely at "1mtnman" pic and you will see 2 bars joining the steps making a more firm platform to climb and no sag in the middle. I think the geometry is different on these too keeping all the steps in line. However, welcome to the world of scissor steps, because there are always some situations where the the steps will slope. I always make sure it is the front wheels I have to block to get level, or else dig down for rear wheels. If I block rear wheels then steps will end up with a dangerous slope on them unless I put a block under the bottomstep, which can have its own perils.