Check that the MSR/MCR magnetic head is not installed upside down or that the track 1 and track 3 signals have not been swapped. While track 1 and track 3 of ISO7810 magnetic cards have the same bits per inch, they have different character sets, different number of bits per character and different start and stop sentinels. If the head is installed upside down, Track 2 could still pass; however, performance may suffer because track 2 on the magnetic head would be slightly misaligned to track 2 of the magnetic card.