I thought it was just me! LA really is a blackhole for the USPS.
Always use the zip plus 4 zip code in large cities. It tells them which driver the package goes to. Even apartment houses have different zip plus 4 numbers for each apartment.
BTW, you would be amazed at how many of my ebay customers screw up their zip code. I check each and every one of the address against the USPS data base for accuracy.