(at around 1h 13 mins) In the abandoned house, a young female zombie with a red dress can be seen lying on the floor with a bullet wound in her head. When the main characters are fleeing the house, she can be seen with the other zombies trying to get in the jeep.
(at around 9 mins) In the beginning scenes of the film, Professor Barrett records himself saying, "Operation Sweet Death must be considered a complete failure. Some kind of degeneration process has occurred which may be catastrophic for everyone. And may god forgive us for what we have produced here and pardon us for this evil we have created." (at around 1h 29 mins) Towards the end of the film, one of the commandos plays Barrett's recording, and the words and tone of voice have changed to the point where it doesn't even follow the same lines as before. The recording repeats the speech as, "Operation Sweet Death must be considered a complete failure. Some kind of degenerate process has begun which could be catastrophic for everyone. May god forgive us for what we have produced and pardon us for this evil we've created." It sounds generally the same but his tone of voice changes from serious at the beginning, to casual-sounding on the recorder's playback. He also uses contractions in the playback speech that weren't used when he recorded it in the first place.
(at around 42 mins) During the Mask Ceremony scene. The masked celebrant takes off his mask and hands it to Lia. This is not possible in a mask ceremony. In a mask ceremony, a man who takes off his mask is no longer considered the man he was before he put on the mask. It is not possible that a man would take off his mask in the middle of a mask ceremony, let alone hand it to an obvious stranger.
The goof item below may give away important plot points.
(at around 1h 27 mins) After Pierre is killed in the elevator. Zantoro shoots at a zombie missing an eye. He clearly fires his machine gun into the zombie's chest. A close up shows the male zombie squirm and fall backward dead from the shots. Which is incoherent because Zantoro (and other characters) know the zombies can only be killed by head shots or incapacitation to the brain.