When the attack on Samoa begins, it is supposed to be right before dawn. However, by the end of the attack it is midday. Since there was a 30 minute timer set right before the battle starts and just finishing up when the battle ends, it is clear that only 30 minutes passed. It should still be just after dawn when the action completes.
In the helicopter scene, the main villain yells at the pilot to climb. He then goes up and throws the pilot out and takes over. It is a common misconception that helicopter pilots sit in the same seat as airline pilots(left seat). Helicopter pilots sit in the right seat. He just threw out someone that wasn't the pilot.
In the scene where a hand grenade is used as a booby trap in Shaw's sister apartment, we see the pin get pulled and the lever separate from the grenade. A few seconds later Shaw put the pin back in the grenade "making it safe." That's not how grenades work. It would have blown up in his hands as the primer would have been activated.
During a fight scene, an actor grabs a hand grenade, puts its striker lever back into place, and replaces the safety pin. Once a grenade's striker lever is released, the chemical time-delay is activated, so replacing the striker lever would not stop a detonation.
When Hobbs and Shaw are in the glass room meeting, Hobbs throws a chair that's next to the table at the glass towards the men on the other side. That chair lands on the floor near the glass, yet when the camera pans after that, it shows Hobbs hand on the backside of that same chair, and the chair is still at the table.