None of the characters seem to have any issues with their hearing despite being in a cramped enclosed space with lots of gunfire and grenades.
A character throws a grenade down a shaft and it explodes into a large fireball. Fragmentation grenades don't have a fire explosion.
At around 23 minutes in, the Marcus Longridge character states the following, referring to his MP5: "Well, it's a rifle, actually". The MP5 sub-machine gun used by himself and the Shirley Dander character are not in fact rifles, but rather, pistol-caliber sub-machine guns.
The Hatch at the end where River Cartwright and Louisa Guy escape from is opened by Shirley Dander from the outside. When earlier in the plot that audience are informed that hatch can only be opened from the inside. However, that refers to its latch, which Louisa does open from the inside. Once the latch is released, the actual lid can be opened from both sides.
At around 11 minutes, the enemy agent slips on the stairs and catches his left hand on a blade placed on the banister. Although, it might be safe for Lamb to think the agent would be holding a gun, he wouldn't take it for granted that the agent would be right-handed.