Layered navigation filters resets on second page

[simas.nnn]

Hello, as mentioned layered navigation filters resets when going to second page, what could be the solution ? Everything else working fine, as pagination and etc. and all filters are applying normal on first page, but when going to second theyre all gone. The strangest thing is that sometimes everything works but most of the time the filters are gone on second page. Please share your opinion, it's very important to us since our shop is working and we have around 6000 products in it...