I'll ad admit to being a newbie step user, I climbed last week and was pleased with the bag. I slung it over my head and right shoulder, pulled out a step with the zipper above the highest step in the bag and for subsequent steps kept the zipper above each one.
When I came down, I packed each step in as I went. Always had the zipper pulled above the level of each step as I went.
I had a 8 step bag, but only had 4 steps and knaider/swaider. Without any fuss or wasted time I was on the ground with the steps already packed away.
The first couple of times I used my steps I had the problems listed by you guys. This time, by keeping the zipper up as described it was easy, fast. The ropes i stuffed in with each step so they come back out on the next climb with each step as I go.
I think the only model needed is to sew under the zipper at the lowest point needed to keep it from zipping all the way down.
Hope that helps.