Other mistake: After the sprinklers go off in the White House, none of the actors' clothes are wet. With the amount of water sprayed, all of them should have their clothes stuck to their bodies. (01:25:00)
Other mistake: Near the end, the sprinklers are turned off in the oval office, which should mean they are all turned off as they all came on together, but where the fist-fighting continues, the sprinklers are still on.
Chosen answer: Grenades generally do not make any sound until they detonate. When you release the spoon (lever) as you throw it, it can make a "ping" sound as its separates from the grenade. No clockwork noises. (I'm ex Army).
stiiggy