Audio problem: At the party when Phil is playing the piano, there are several shots of the other band members. Multiple times they are seen playing their instruments, but they are never heard. The most obvious example is right before Phil finishes up his set. The saxophone guy is playing but you never hear it.
Continuity mistake: When Phil looks out the window on the first Groundhog Day, he sees the right-turning truck outside the window just as the radio people shout "Groundhog Day.", but on the first repeat of the day, the same scene outside the window occurs only after this exclamation is made. It couldn't be altered by him because he had just woken up.
Deliberate mistake: When Phil wakes up at 6 AM, it's already bright outside. At 6 AM in February, it would still be pitch-dark. This was done intentionally by the director for the sake of the viewer, but still makes no sense.
Continuity mistake: When Phil comes around the corner, just before meeting Ned, there are two women walking together in the background. The one in blue is holding a yellow sign upside down that says Phil (the groundhog, not the character). The first 3 days in a row they are together as they should be. On the forth day and every day thereafter the woman in blue is by herself which does not follow the exact day sequences.
Continuity mistake: In the shot where Phil, Gus and Ralph exit the bowling alley, Gus is having trouble putting on his coat and leaves his tee shirt exposed in the back. After he takes Ralph's keys, he walks away from the camera, his jacket is straight and his shirt pulled down.
Visible crew/equipment: After Phil drives the truck off the cliff, and it explodes in a burst of flames, there is a shot of Andie MacDowell and Chris Elliot staring in shock at the disaster. The two actors are bathed in an orange glow supposedly coming from the flaming wreckage. But in the lens of the TV camera Elliot is holding, there is a noticeable reflection of the lighting equipment used to create the glow effect on the actors.
Visible crew/equipment: When Bill Murray first meets Ned Ryerson, there is a reflection of the film crew very briefly in the shop window behind them.
Other mistake: When Phil is driving the car against the train he ultimately swerves out into a railroad crossing. However when the approaching train is shown from within the car in the last seconds before the two vehicle would collide, there is no crossing to be seen on the remaining track stage between them.
Revealing mistake: When Phil escapes the police with his drunk friends in the car, their stunt doubles' different faces are visible as they start driving on the tracks.
Revealing mistake: When Phil drives the truck off the cliff, you can see right through the grill of the truck (meaning there is no radiator or engine), and the transmission is also missing, as you can see when the truck is falling upside down. Without an engine or transmission it would be hard to drive off a cliff.
Continuity mistake: At the end of the movie when Rita reaches over Phil to turn off the alarm clock, we know the clock always goes off at 6:00AM. After turning off the alarm 2 1/2 minutes go by while they are talking and the clock should read 6:02, but when the camera pans to the clock it only reads 6:01.
Continuity mistake: Right after the scene where Bill Murray gets hit in the head with the shovel while talking on the phone, there is a shot outside the bar where Bill is inside drinking and it is night time. In the scene following, Bill is taking a shower for the first time. While Bill is in the cold shower, it is day time outside of the window but it should be night time because he hasn't woken up a 2nd time yet.
Continuity mistake: When Phil first meets Ned, right as he asks 'Did you turn pro with that belly button thing' there's a close shot of Phil where a man with a yellow hat and red collar walks behind him. In the very next shot, we can see the same man approaching from further down the street, then passing behind Phil again.
Continuity mistake: When Bill Murray has stolen the Groundhog and is driving away with it in the red truck, the police car and the TV van chase it. There is a shot of the red truck going under a low bridge, and then a long shot of all 3 vehicles. There is no way the TV van could have gotten under that bridge with all the stuff on its roof, and yet in the very next shot it is seen continuing the chase.