I bought it new 3 years almost 4 years now. Worked fine until now It just will not stay down when I push it down on any of the ajustments. It's like it is off its traks or the thing that holds it down is worn out.

I have a Koala also and the times I have had difficulty going down and staying down was when a cord was in the way. I know that sounds elementary but have you checked for obstructions? Good luck.