What causes packages to not be processed properly?

We process large volumes of packages daily and have a very small percentage of problem packages. The most common cause of these problems is an incomplete ShipitAPO address on the label. This means that the address is missing an EXACT ShipitAPO owner name and/or missing an EXACT matching ShipitAPO account number. This causes a tremendous amount of investigative work on our part, as we can never simply guess about the owner of a package. The other cause of problems includes us receiving packages that the United States Postal Service will not forward (due to size, weight or content restrictions).