My google accounts kept disappearig.

It is been like 6 or 7 months now since i move to new pc and i been using firefox in this new pc together with other browsers. I am not really using firefox for anything related to google or gmail but just other website that have 0 relation to them. But i have still logged in my main accounts in firefox. It is been twice that once in a while, when i have to check my gmail accounts, all of them disappear and all i see is just sign in page only. There is no log in again or Please log in to this address or that address but straight up fresh page of google sign in page. I still logged back in when it first happened because i heard about the bug that happened with firefox update but now it happen again. It is as if my cookies just vanished but no, other sites still got their own cookies and there is many cache of other website here. other than my google accounts. What is happening here. Is my firefox bugged or something? Should i reinstall and have to relogin everything "again?"