There are several witnesses to the count so if there was something drastically wrong regarding spoilt papers I think it would come out.
Many years ago I voted for Jimmy Perchard and Bob Hill thus spoiling my paper, but I can say I voted for them, I had the only spoilt paper in St Martin, since then there have been I think at least 7, not sure how many this time. I think the rise in umber is just voters voicing their dissatisfaction, nothing more.