after playing 500 games in diamond1/2/3 I still lose 60lp in a single game

In almost all games, the more you play, the more stable your ranked position become. Your mmr/lp won't change much if you play a lot of games and proved to stay in a division. Only in this game it's different. like wtf is this 60lp loss? In one single game I drop over half of a rank. Even after staying in d1/2/3 for 500+ games the matchmaking system still smh thinks I belong to a lower rank after a single loss. This is really frustrating.