Countless bugs are destroyed by the perimeter burn, yet in later scenes there are none.
When Sandee is talking to Joe, he is holding a q-tip to her chin. In the very next shot, he is just bringing the q-tip to her chin.
(around 59 min) a character is shuffling some playing cards, and then holds them in his left hand, revealing the Ace of Spades at the bottom of the deck. He then picks up a lighter in his right hand and lights a cigarette. There is a cut to a different angle as he puts the lighter down. In that shot the Ace of Clubs is at the bottom of the deck.
The alien "bugs" are often referred to as arachnids; starting with the scrolling updates at the beginning of the film. The bugs in the movie only have 4 legs; even if you counted the 2 smaller "stabbing pincers" that would give them 6 total. All arachnids have 8 legs.
When a trooper is dragged away during the attack on the outpost it is obvious she is being pulled by wires, as the bug is simply backing up with her. For much of the shot it is not even touching the trooper.
During the bug attacks on the abandoned outpost, targets on the squad's portable radar unit move onscreen between rotations of its sweep arm rather than appearing in different static locations with each new sweep.
For some reason all the Mobile Infantry patches on the jackets are sewn upside down. The MI is now WI.
When Dax says "Murderer's don't go home," his mouth stops moving half way through.
No one wears rank in this film except for the General, but he does not wear the Federation rank shown in the first and third films; instead he wears a US Military single star insignia. Since no one wears rank insignia, no one should know what rank to address them with.