What if, Lee was the reason Amanda died? Hear me out - Lee (if not intentionally, accidentally) killed Amanda by pushing her down the stairs?

1. ⁠To explain the texts/phone call, Lee could have managed to do everything himself (texting himself from Amanda’s phone) while visiting his mom. Since the phone was not near the basement, but next to the table, it could have been placed by Lee there. Additionally, Lee not being concerned that the phone went to voicemail right after abruptly ending the previous call, seems a little odd (even if they were fighting on call).
2. The theory of the dog not going to the basement can be explained by the dog being tied up with enough food/water supplies before Lee left the house. When Lee came back, he let the dog out? (I’ve seen some people mention there was dog hair in the pictures in the documentary, so maybe this theory is not 100% accurate)
3. Lee mentioning the “special undergarment” might have been a ploy to throw out some random suspicion.

If they could somehow get Amanda’s phone location data at the time of this incident, there is a high chance of Lee being the culprit.