I have to watch or the backstop will go under the bag not over. Try putting a couple of loads in without much tension this fills the bag and lets it set flat on the ground then put the pressure to it. This is how I have always done it. I rarely get a bag where the back stop lifts up this way.
I will say this too. A Kelly Ryan bagger works fine but is not quite the bagger as other makes. AG Bag and Versa are a much better bagger. IF you look the back stop is made different on those brands too. Matter of fact most Versa ones do not even use and external back stop and cables.