When Jen meets her father for the first time in the woods she runs and slips on the ground and her jeans are dirty on her knees. A few shot later when they run to the canoe her jeans are clean.
The movie/TV fallacy, "Police won't investigate until a person is missing more than 24hours," is used.
At 53:55 and 54:07 you can see the scope cap is fitted to the rifle so Tommy couldn't have seen anything through it.
Tommy does CPR on Mikey incorrectly. He forgot to do the breathing.