During the opening cinematic, while Hunk's team is being decimated by Birkin, a commando is shown cowering backwards in fear while firing his MP5. On top of the weapon there is a form of red dot sight, possibly an aimpoint. When Birkin impales the hapless commando and the gun goes flying, the scene cuts away to a shot of the gun hitting the ground in slow motion while still firing. In this shot, the scope/red dot sight is no longer present.
The goof item below may give away important plot points.
In the scenario Decisions, Decisions, the UBCS Sergeant Nicholai is seen performing various objectives around the Raccoon University area up until the countdown for the nuclear missile strike to destroy the town starts. However, at the same time, Nicholai was trying to kill Jill at the dead factory just nearing the edge of town; even if he survived in the end, he could not have been at two places at the same time due to the countdown.