If there are 8 I/O pins controlling the array, this means that there will be 6 parasitic paths through pairs of 2 LEDs, and 12 LEDs may be unintentionally lit, but fortunately this will only happen when the one bad LED is supposed to come on, which may be a small fraction of the time and will exhibit no deleterious symptoms when the problem LED is not supposed to be lit. If the problem is a short between nodes "x" and "y", then every time any LED "U" with either "x" or "y" as its anode or cathode and some node "z" as its other electrode is supposed to come on (without loss of generality, suppose "U"'s cathode is connected to "x"), the LED "V" with cathode "y" and anode "z" will light as well, so any time EITHER node "x" or "y" is activated as an anode OR a cathode, two LEDs will come on instead of one. In this case, it lights only one additional LED unintentionally, but it does it far more frequently; not merely when the failed LED is supposed to come on, but when "any" LED that has a pin in common with the failed LED is supposed to come on.