A character appears to have superhuman strength. She wields a metal bar as if it weighed no more than a plastic replica.
One of the group is stabbed in the stomach and Kat, a former paramedic, asks for something to lift her feet up. Usual first aid practice is to elevate the wound, ideally above the heart, to reduce bleeding. Elevating the feet would return blood to the abdomen, thus increasing blood loss.
A character is dependent on high dosage Percocet / Vicodin painkillers but has no idea whether she has enough for the duration of the trip.
The walk leader berates a group member for arriving at the bus barefoot, not in boots. She then tells them the walk will start 250 miles away, five hours' drive. Nobody needs heavy hiking boots to sit in a bus for a long journey.
On finding a cabin, a character says "So much for the middle of nowhere". They have been walking on a clear path with stone steps and well-maintained wooden bridges. Even for a city dweller this was never the middle of nowhere.
In the opening scenes two men are walking through a forest, apparently spraying paint on trees in an attempt to find their way home instead of using a map or established paths. They arrive at a large clearing with a single tree in the centre, surrounded by miles of dense woodland, but one asks the other to 'tag' the tree, as if they might not remember it.