(at around 1 min) In the office scene where Boggs keeps drinking, he sets the bottle on the file cabinet with the label facing away and half full, then when he goes to pick it up again the label is facing forwards and the bottle is three/quarter full.
In the Dodger Stadium scene, the close up shows a Dodger pitcher #20 (Don Sutton) throwing a pitch, but in the following wide shot it's a Dodger batter and New York Met pitcher completing the play.
Hickey and Boggs have to sneak into the football game disguised as ushers because the game is sold out yet there are quite a few empty seats, including entire rows, during the game.
Sold out doesn't mean full seats just tickets sold. Companies buy blocks of tickets and don't always use them plus individuals might buy a ticket but don't make it to the game.
During the final gun battle, the title characters take cover behind two cars, a Firebird and a Rolls, which get shot up. The bullet holes visible in the latter don't look like the popular perception of 'clean' round bullet holes in metal, but splintered like wood or GRP (glassfibre).