In the partof the movie where Donkey and Shrek are going to free the princess to bring her back to Lord Farquad and they are crossing the rickity bridge. Well, look closely when the board beneath Donkey breaks. It shows it breaking in half and then it shows it as one single peice.
The wood breaks in two, but only one half falls. If you look closely at the bridge when it closes up at donkey looking scared the other half is still connected to the bridge on the right.