I have the same type of power lift on my Flagstaff and it is a P.I.T.A. to say the least. Mine doesn't close all the way but is will lower about 2-3 inches.
I had to take the plastic plug off the side that exposes the gear mechanism and when I get it to the height I want, I just shove something in it to keep is stationary.
There has to be a better way, but I haven't figured it out yet.
Courage is the feeling you have right before you fully understand the situation