Keep folder state is unreliable

[Kaan88]

I still haven't figured out how it works. I click on the category, uncollapse it and then refresh the page and it collapses again. I try it again and this time it works or not. It seems completely random. Right now I'm unable to collapse a folder no matter what I try.

I've tried collapsing it while on the main page, while in the category, tried refreshing the browser after or just clicking main page. It remains uncollapsed. I'm using firefox.