As I said before, it is not uncommon to see marriage register entries for marriages that never happened, as the registers were often written up in advance to save time on the day. Normally, these unfulfilled entries are crossed through, but transcribers may well ignore this and copy them as if they happened. This fits well with the fact that the earlier entry was not passed on to the local registrar and thence to the GRO.

The child being registered in the maiden name if the mother is another clear indication that no marriage had taken place, rather than there being some residual doubt about its legality.

Best of luck in Matlock. If you are really, really lucky there may be a marginal note giving a reason for the cancellation. If there isn't, it might be worth seeing if the relevant banns book has survived.

Caroline