Other mistake: In the last game, Chet pitches six innings ("You gave me six great innings!"), then Henry takes over pitching, meaning he'd be pitching in the 7th inning. Sounds good, until we fast forward to the 9th, with Heddo batting with two outs... Assuming Henry was perfect, Heddo would be the 9th batter Henry faced, meaning he would've been Chet's last out in the 6th, which of course he wasn't (the Chet play at the plate ended the 6th and he wasn't facing Heddo.) Also, Heddo was seen walking up to the plate after the second out of the inning (the rundown at second base), with Martinella saying something like "holy goosebumps, it's Heddo" as he approached. Heddo would've been on deck, so it wasn't a surprise, plus he would've already been at the plate prior to the rundown play.
Suggested correction: There is a reasonable explanation for both of those points. Heddo could have been a substitution player after the sixth inning, or be a pinch hitter, so hadn't been to bat yet. This would be logical since Heddo is a fastball hitter and they think Henry is still throwing fastballs, so as a last ditch sent him in. For why they didn't notice that Heddo was on deck, they were captivated by the on-field action, and with Henry off the mound going over by first base and doing stupid stuff, hadn't looked over yet to see who was next.
Revealing mistake: When the boys take the boat out, almost every shot shows smoke coming from the rear. If you look closely, the smoke isn't coming from the motor but next to it.
Suggested correction: The smoke is coming from the motor, escaping it through the side, which makes it appear to be coming from elsewhere.
Factual error: When the game is being played against the Dodgers, the sun is in the outfield and putting shadows facing towards home plate and the batter which is illegal in the rules of baseball. The sun can not be in the batter's eyes. This same mistake has happened in other baseball movies too.
Suggested correction: While it is a recommended rule (MLB 1.04), it is not against the rules for a stadium to be aligned any way. As seen here, many stadiums are aligned differently. Https://www.baseball-almanac.com/stadium/ballpark_NSEW_NL.shtml#:~:text=Major%20League%20Baseball%20clearly%20states,1.04%20to%20be%20ignored%20by.
True, however all stadiums are built with home plate on the south, north or west sides of the stadiums (including SW, NW) NO stadium has home plate on the EAST side (or NE, SE, etc) for this specific major rule.
Continuity mistake: At the party, Larry talks to Jack. Jack is looking directly at Larry but the scene switches angles and Jack's head is tilted down instantly.
Audio problem: When Henry is at bat, his mother is berating the pitcher. She starts saying you stupid mother... and it cuts to Gary Busey completing the sentence. He says "God damn," but his mouth doesn't match. Chances are he said the f-word but it was changed in post for ratings issues.
Continuity mistake: While flying on the road trip, the interior shots show a widebody aircraft with twin aisles. The exterior shots show the much smaller 727, which only has a single aisle.