During the intense skate scene on the building site, Slater's skateboard miraculously changes from a regular skateboard to a freestyle board, which is less wide and differently shaped than the board he rides throughout the film.
When Brian is sneaking into the WMS warehouse you can clearly see a number of times his skateboard he had throughout the first half of the movie. He then sacrifices the board to blow up the propane tank.
A few scenes later when he is riding in the street with his backpack he has the same skateboard, then breaks the trucks on the police lights. Only then does he replace it for the new black board.
During the downhill chase scene with the motorcycles, Brian ollies onto the top of the cop car knocking off the lights. In the next shot, the cops look up to the roof of their car and you can still the bottom of the lights, still intact.
After the skaters are told that they have to head to the intersection of Harbor and Katella, they go into a residential neighborhood. In actuality, Harbor and Katella are major thoroughfares in Anaheim, and the intersection of Harbor Boulevard and Katella Avenue is within walking distance of Disneyland. In fact, Harbor and Katella were the nearest cross-streets to the Cosmic Age Lodge where Vinh is killed earlier in the film.