Visible crew/equipment: When Peyton is looking for Emma and Joe, she walks into the bathroom. When she turns the corner, you can see the camera man, in the reflection of the mirror, above the sink.
Factual error: The glass shattering and falling in the greenhouse would have been unlikely to kill Marlene, let alone even cause that much damage to her, as the glass would have very little to no time to gain more force, falling at that low of a height. And if Marlene were to be killed, she would have probably bled out over time, as opposed to almost instantly dying as the film implies.
Peyton Flanders: When your husband makes love to you, it's my face he sees.
Question: How did Peyton get back in the house at the end without keys?
Answer: She probably had another key made.
Answer: The same way any common criminal gets in to a house, she "broke" in by either kicking the door, or smashing a window, etc. A locked door is not that hard an obstacle to overcome.
Jazetopher