Re the sliding door - in JM’s tour of the property and demonstration of the sliding door, I didn’t find it exceptionally quiet. It sounded like all sliding doors, imo.
Another thing about sliding glass doors, you don’t just hear them, you sort of feel them. It’s like there’s a vibration thru the walls. I would think that vibration would be even more noticeable in a mobile home, given the less sturdy construction.
I don’t personally believe those children went out the sliding door. If they had, I find it hard to believe they closed it behind them all the way.
IMO