Have you ever had pain in your lower back while leg pressing?  That pesky machine can be a little difficult if you aren’t consciously aware of your posture while sitting in the contraption.  Check out this video by 
Nubreed Nutrition Athlete Jasen “Nubreed Freak” Ono, on the proper way to leg press.

Try it out and see if you can bust through that plateau that you’ve been stuck at.