At about 1hr 19 mins, the upper-right AED pad is shown on Brett's very hairy chest and is clearly not in contact with the skin. The pads won't stick to a hairy chest, so AED units are equipped with razors to shave the chest so the pads will stick.
At about 39 mins, Jen explains that the room needs to be dark because it takes more energy for the spirits to manifest themselves in the light, yet although the electric lights are off, the Venetian blinds are open, admitting a fair amount of light.
In the beginning of the movie there was a pregnant woman who is injured in the hospital and they are bagging her with an ambubag. They didn't have to do that since she was obviously talking, meaning she can breathe fine.