Revealing mistake: When the Level 3 Sentry is firing up into the air for no apparent reason, it fires some rockets with a clear defined smoke trail behind them and disappear off screen. Then the shot jump cuts to further away and suddenly the smoke appears again, but the end of the smoke trails are solid and crisp indicating the animators used the smoke animation as if the rockets had just been fired from that spot... in the middle of the sky. (00:01:10)
Continuity mistake: Towards the beginning of the video and just a little bit later, you see bullets hit the truck behind the Engineer and leave clear, large bullet holes. These holes are very visible and stay in the same spot. But as the camera is pulling back and you see these large holes still there, you can see sparks jump off the truck a couple more times in two more spots near the Engineer's head. However these shots leave no holes while the older holes remain visible. (00:01:10)
Factual error: It is a Level 2 Sentry that is sitting by the Engineer on his left. But as the camera pulls back, and then does a jump cut further away, the Level 2 Sentry is seen suddenly firing rockets. But only Level 3 Sentries can fire rockets. Also it's still pointing to the right of the screen and shooting bullets visible while the rockets fire towards the left of screen. Even Level 3 sentries can't fire in two different directions at once. (00:01:15)
Audio problem: As the camera pulls back from the truck, a Pyro is running up at the Engi from the left side. When the Level 1 Sentry turns and kills him, the Pyro makes the Sniper's death cry. (00:01:10)
Character mistake: As the camera pulls back from the truck, the Level 3 Sentry on the ridge looks up and fires rockets into the sky for no reason while the enemies are advancing from in front. (00:01:10)
Factual error: When the Level 2 Sentry gun begins firing, you can see Shotgun shells falling out of it instead of the usual ammo casings. (00:00:40)
Character mistake: When the Level 3 Sentry gun is revealed on the right of the screen and fires a rocket barrage to the left, you hear it explode as the Engi looks over. You then hear Scout scream "My arm!" really loud. Then an disembodied arm falls in front of Engi with a plop. However, this arm is from the character model of Sniper, not Scout. (00:00:45)