Only one dropdown works (but is weird)

Hi

I have two dropdowns next to each other with two different categorys. The left one works, but when I go back it skips the page I was on and goes two steps back. Very weird… you can check here:

https://in.sinkadus.com/collection/

If you use the tag-cloud for “Teknik”, you can go back to the page before, no trouble. But if I use the dropdown, back takes me two steps back… why? how?

The other dropdown, for “Material”, doesn’t work at all. But everything is EXACTLY set the same as teknik. Tag cloud works fine.

What am I missing here?

Thanks for listening..

The page I need help with: [log in to see the link]