I never stay logged in on my desktop + notebook

I'm using Firefox on Arch with ublock origin, umatrix, decentraleyes, darkreader, bypass paywalls, old reddit redirect.
None of these should affect Tildes in any way. but still, Firefox seems not to be able to keep me logged in, and everytime i open Tildes in a new tab, I'm logged out. Sometimes it remembers the theme (solarized dark) sometimes it does not and only remembers it after a refresh, and sometimes it just dont.
I dont even know where to look for a solution, especially as this seems to be Tildes specific as no other website seems to have this problems. an I'm pretty shure it has something to do with my Firefox, as it is that way on both of my computers.

edit: solution was to delete all tildes.net cookies