IMDb stopped working properly on Firefox

For a few days now, imdb has been unusable on Firefox. It seems like all scripts on the site stopped working: I can't open any dropdown menus, see my own movie rating, play trailers or use the watchlist function, etc. I disabled all browser add-ons as a test, but no improvement. The only thing that worked was to open imdb in a new private tab, or use a different browser such as Chrome. I'm using the latest browser version (142.0 (64-Bit)) and haven't changed anything, so what's the cause of the problem?