Character mistake: The prescribing doctor or a nurse should have given Matt/Joey's mom instructions on the proper use of an oxygen mask, but she did not demonstrate this. She picked up the mask, put it over her nose/mouth, and immediately inhaled ONCE followed by removing the mask. About a minute later, she repeated these ineffective steps. Instead of inhaling the oxygen, she was most likely simply inhaling "regular air" in the room - she did not keep the mask on long enough to enable release of oxygen.
Don't Tell a Soul (2020)
1 character mistake - chronological order
Directed by: Alex McAulay
Starring: Rainn Wilson, Mena Suvari, Jack Dylan Grazer, Fionn Whitehead
Other mistake: In the opening scene where Joey is breaking into Ms. Dillard's house, he quickly smashed a window with his flashlight and immediately crawled through the window - without checking to see if shattered glass fragments were still in or around the frame. Despite his carelessness, he did not even get a cut on his hands or elsewhere, which would be almost impossible under the circumstances.
Trivia: Many people are familiar with the "Stockholm Syndrome" wherein hostages or kidnapping victims develop a connection with their offenders - they identify with or feel empathy for the people holding them captive. The "Stockholm Syndrome" is also known as "capture bonding." Its lesser-known opposite (or inverse) is called the "Lima Syndrome" - the hostage-takers or kidnappers start identifying with or "feeling for" their victims; they bond. This movie portrays BOTH, but with a different crime.