It's not the vector, Victor -- it's some kind of translation error in the software.
I often notice minor discrepancies between CDU (PROG, POS REF) and ND values. There are even discrepancies between the left and right side. Depending on whether or not you have GPS to minimize the errors, you may notice them more if there is a discrepancy between the system feeding the left and right side at the time.
Next time you see something like that, compare the ND values with the "master" CDU (usually left), and see if they're closer.