Revealing mistake: In the scene where the town is collapsing, there is a shot of Ben in the bathtub falling into the river, if you look closely, you can see the strings that are keeping the tub steady and upright.
Revealing mistake: In the climactic scene when the whole town ends up in Ben's and Pardner's tunnel system, including the brothel where young Horton is once again exploring his limits, the bed with Horton and his lady of choice falls on the street. When it topples over it's obvious that both Horton and his sparring partner are tied to the bed. (02:23:20)
Revealing mistake: When the tunnels start collapsing, all manner of buildings come crashing down; one of the buildings, upstairs, has a couple in bed; they come flying out and they land face-down with the bed on top of them. We can see the man is tied to the bed - to stop him being injured, I assume. In the next shot, the bed is on the ground and the couple are lying on top of it.