In the last 10 minutes of episode #2.10, "Skinwalker", Lex Luthor's sunglasses disappear and reappear between shots while he is talking to his father.
During the dirt bike scene the engine sounds constantly change between 4-stroke and 2-stroke engine sounds.
In the run-in with the foreman, the professor asks how he can be trespassing on "land my people owned for thousands of years." No Native American nation used European traditions of land ownership prior to colonial times, and a tribal member wouldn't have used that phrase.
Building on top of caves would be too risky. Buildings need foundations and buildings that large have sub floors. Having the ground full of caverns would make that a difficult task. On top of that a cave system would be a very unstable foundation to build on and the building would run the risk of falling into the ground. Even if they built the sub floor into the cave down to the cave floor the building team can't be certain there aren't more caves underneath. The entire project would have been moved or canceled upon the discovery of the cave system.
At 6 seconds in the Luther Corp Sign reads Corporate Plaza The "Leeder" in High Tech Office Space instead of Leader.
While Clark and Pete are riding dirt bikes, you can see a crewmember in a green jacket in the bottom-right-hand corner of the screen in the shot where they go off the jump. In the next shot he has disappeared.