I would have to agree with eyeonwall, that this was caused by ink contamination.
Although it is most likely just the red ink that mixed with the black. This can result in a brownish or maroon color.
See the pic below of the #702 "Red Cross" issue. Which in this case, the black ink contaminated the red ink of the cross, but the results would be similar.
I have seen the #702 error with various shades depending on the amount of contamination.