I think it is an oversimplification to assume that 0 was a viable outcome in addition to the number of entries. It is far more likely to be an off by one error, but (given YoshiP's post) it may be a more nuanced problem with how the calculations are done.

What happens next will depend on the precise cause. If it's simply an off by 1 error, then that's great... and not, because it meant the house went to the wrong person. In any case, those plots with only one entrant have a fairly obvious solution. The question will be how the team decides to implement any sort of redress. But I doubt they'll leave people who actually had to compete with others in the lurch.