Catcher drops the third strike, but the hitter gets to first base. Is this an error on the catcher because the batter reached base because of the drop 3rd strike?
“The umpire -could- call the catcher with an error…” Umpires don’t charge errors, official scorers do. Scoring is not the umpire’s responsibility. Since catchers and pitchers handle the ball so much during a game, they are often charged with passed balls (catchers) or wild pitches (pitchers). Each is its own category and neither count as errors. In your play, credit the pitcher with a strike out and charge the catcher with a passed ball, but not an error. Here is the portion of the official rule that answers your question: 10.13 Wild Pitches And Passed Balls (b) The official scorer shall charge a catcher with a passed ball when the catcher fails to hold or to control a legally pitched ball that should have been held or controlled with ordinary effort, thereby permitting a runner or runners to advance. When the third strike is a passed ball, permitting the batter to reach first base, the official scorer shall score a strikeout and a passed ball.