[charrisTTI]

Try reversing the channel assignments. Move encoder 5 input to 3 and 3 to 5.Move encoder 6 input to 4 and 4 to 6. Does the problem move with the encoder hardware? If it does, then you have an encoder problem. If problem stays with 5 and 6 then you are looking for software problem. Does problem vary with speed? Is everything ok with slow rpms? What if you only run one motor at a time? Are the counts accurate? Problem may also be with the interrupt dispatch code. You did not post that section of code.