I never had to deal with this issue myself so I can't be of much help, but since nobody more knowledgeable has replied yet, here are my two cents:
As far as I know the game servers regularly try to communicate with the anti-cheat client on your PC. If this communication fails, your connection is terminated for obvious security reasons.
Maybe this is what's happening to you. Have you tried to reinstall the anti-cheat? If you own other Battlefield games protected by Javelin (BF1, BF2042, BF6), are you able to play them or do they also disconnect?
By the way, minor detail but the game has been using Javelin for two years now. Originally it was called "EA Anti-Cheat", then last year they rebranded it. If your issue is actually tied to the anti-cheat and it only started six months ago, then it was probably due to something changed with an update, rather than the anti-cheat's existence as a whole.
