There's been a few posts today from people experiencing this same issue. I'm going to tag a community manager.
u/Braddock512 u/PartWelsh Have you guys noticed these posts? Several posts today from people logging in to the game today and having their ranks reset to lower levels.
Additional posts:
https://www.reddit.com/r/BattlefieldV/comments/jnx86q/my_friend_has_recived_a_downgrade_leveling/
Edit: Yet another one:
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