Audio problem: On the oil rig at the start of the movie, the 2 actors monitoring the deep sea submarine's progress are subjected to a major explosion noise - yet they don't even notice it. Only when the 2nd explosion comes and rocks the whole rig do they react.
Plot hole: The robot pilots have no screens/monitors in the robots to show them what's outside - only some obviously unimportant text or graphics. How could they fight the monsters without being able to see what's in front of them (or anywhere else, for that matter)?
Plot hole: When the robot pilots first connect after the first attack, Red tells the story of his battle. They don't seem to even notice the dozen or so civilian bodies they have to actually physically step over - and the bodies are just lying there along the sidewalk & parking lot; no signs of any monster attack, so how did they die?
Continuity mistake: Admiral Hadley's "war room" has a digital clock which the few times we see it is always set at 3:02.
Factual error: At the start of the movie, the oil rig discovers the first monster. The characters reference the seabed there being at 800 fathoms - which is pretty deep; they'd have to be hundreds of miles or so offshore for the ocean to be that deep. However, the oil rig is just a few miles off a coastline, as the background view shows.
Continuity mistake: As the movie ends, the heroes walk from the trashed red robot towards the ambulance & trucks, and the woman sitting in the ambulance has a blanket over her shoulders, then there's no blanket, then it's on her knees, then her shoulders, then it's gone...
Factual error: Admiral Hadley often barks orders ordering Army forces to act, not just Navy forces. He wouldn't have the authority.