I have never in my life seen a prefabricated computer patch cord that was terminated on both ends with 568A. If I bought such a cord, I would return it because whoever made it did not know what they were doing, in my opinion.
You also need to check the markings on the outside of the cable to make sure it is of the appropriate construction. If it is not stranded and marked for IEEE category (3, 5x or 6x) and UL type (CM, CMR, CMP etc.) return it. Unless you like to work overtime for free diagnosing unexplained problems.
