When Shaun the sheep is walking along the ladder towards the motorcycle, Wendolene shouts "Be careful, Shaun." However, Shaun is simply a nickname that Wallace has given him and he has never been called that in front of Wendolene, so how does she know his name?
When Shaun is being washed in the basement, the Knit-O-Matic malfunctions and switches the setting from "Wash" to "Light Shave". After Wallace tells Gromit to do something, you can tell by the lights on the settings that the Knit-O-Matic is still programmed to "Wash". When we see Preston's point of view from where he is hiding a few seconds later, the Knit-O-Matic is once again programmed to "Light Shave".
When Gromit unwraps the jigsaw puzzle box, the label indicates it contains 5000 pieces. While he finishes laying the puzzle, the upright box now shows the number 500 on the label, and when he reads the puzzle's message, there are just 13 x 8 = 104 pieces on the table.
When Gromit climbs up the ladder during the motorbike chase, he places the base in the sidecar. When he grabs the cables, Wallace grabs the base of the ladder as it rises; after they finish the spin, Wallace places the foot of the ladder in front of him.