During dinner with the reverend, dishes move around the table between shots.
Marc pours wine from the Blue bottle, then caps it. Subsequently it is seen both capped and uncapped.
During the last supper, the green bottle gets emptied by the "left wingers" then when they are shown from different camera angles it's full again, then empty, then full, then empty again.
During the toast at the dinner with the reverend, in successive shots of the reverend and the other diners the reverend's glass alternates between being held in his hand and resting on the table.
Pete and the sheriff refer to Pete's shotgun as a "rifle". A rifle would not be used for skeet shooting, nor would a skeet shooter or the sheriff confuse the two firearms.
The sheriff finds Pete's car with the shotgun laying on the backseat. She doesn't charge him with a crime since he has a "license". No license or permit is required to own or transport a shotgun in Iowa. However, it is illegal to transport one without it being locked in a case or disassembled.
When the group are discussing the number of people who were killed, they waiver between 9 and 10. Pete reveals a cast that shows 10 tick marks which would make the total so far 11 - because the first character killed, Zach, wasn't counted. However, up until this point, you only see that there were 8 total murders so far. A look at the credits demonstrates that other victims - an "immigrant hater" and a "skinhead" were cut from the film.
When the group is arguing after Luc stabs the woman who hates Catcher In the Rye, the victim is supposed to be dead with a knife in her back, slumped over the chair, but she can clearly be seen breathing.
After Norman Arbuthnot lit his cigar at the end of the movie, he is checking on the Iowa Tribune newspaper. He stops at an article with the title "Nine Other Locals Missing and Feared Dead". The subtitle still fits to the title but the content of the article itself does not. It is describing the halt of the construction of the worlds largest particle collider.