The turrets at Anvil Gate are not of the same type as seen in Gears of War 3 despite taking place at the same time.
Rather than swap, the weapons completely are mirrored when they switch hands, and thus the empty cases eject on the other side of the weapons and the bolts are flipped.
When picked up in cutscenes, the fabricator can be in a different direction from in between cutscenes.
The Hammerburst rifles as seen in Gears of War 3 were single shot self-loading rifles, yet the ones found at the bottom of the mine shaft - and in flashbacks leading back to the events of Gears of War 3 - fire 3 round bursts.
It was said that the settlement was without power, yet an electro-mechanical siren can be heard blaring when it is attacked.
The maximum ammunition for each weapon should be a multiple of the capacity for each magazine, since it doesn't make sense to have partially filled magazines; however, the maximum ammunition doesn't always equal a multiple of the magazine size for each weapon.
Marcus Fenix has claw hammers on his workbench. Claw hammers are typically used for home repairs and not gunsmithing.
An aeroplane the size of the Vulture aeroplane shouldn't be able to match the speed of a motorcycle without stalling.
The power is on at the Fort despite it having been abandoned for a long time.
When designating targets, the Player's character may name the enemies even before the enemy has been named in the in-game dialogue.
A detail going to the fort to bury thousands of Locust bodies would probably have buried the bodies of COG soldiers, yet COG soldiers' bodies can be seen strewn around where they fell in battle.
One of the collectibles is a newspaper explaining that crystallized Locust bodies are dumped off at classified locations. Despite being mentioned in newspapers, only Marcus Fenix seems to know about them being crystallized.
An EMBAR sniper rifle can be found on top of the dam, despite there being no DB units there.
In the dam Kait tells JD that there is a switch to extend a breaker, but it is a wheel, not a switch.
If he accidentally shoots an ally, JD might say 'Misfire, sorry!'. A misfire is a weapon going off accidentally, not friendly fire.