Deliberate mistake: Ash's car breaks out into the courtyard and the whirling, windmill thing batters the Deadites aside. We see the carnage a couple of times filmed from different angles, one Deadite, planted, legs apart, gets battered twice and the guys who come in from the left and are quickly jerked off screen are shown again seconds later.
Deliberate mistake: During the final battle, when Ash is driving around in his car with the giant fan mounted to the front mowing down enemies, some of the evil skeletons he runs into aren't moving at all for several seconds before being hit. This reveals that the were just props designed and set-up to be run over for the effect. Additionally, the first two sets of skeletons he chops up in the fan are the exact same skeletons shot from different angles. (You can tell from the distinct way the one skeleton's arm comes off and ends up on the car's front).
Answer: Towards the end of the film, when Ash mounts his horse and rides off into the sunset (before it then cuts to present day and he's back at the S-Mart), you can see his chainsaw is strapped to the horse's saddle. It seems that he either recovered it after the battle or perhaps he sent someone to the windmill to retrieve it.