The Spectre has a completely different origin than in Doom (2016).
Grammar mistakes in subtitles.
Apparent Bug: Switching between weapons after firing somehow ensures that the weapons are loaded when the Player switches back.
The view through the scope of the heavy cannon does not match what the display looks like when zoomed out.
The fortress appearing from behind Earth should, at that aspect, be thousands of miles from top-to-bottom, but it is much smaller than this.
An elevator is shown to fall. Elevators are designed not to fall.
The crystal power-ups happen before the Doomslayer even takes hold of the crystal.
VEGA tells the Doomslayer that his super shotgun was hidden by the Hell Priests. They could have simply destroyed it rather than hide it from him, yet why they did not do this is never made clear.