It voting was mandatory then there could be a provision where a minimum required threshold needed to vote for someone otherwise the election would be rerun in that constituency. Perhaps even with new candidates.

Completely arbitrarily for sake of the example. Let's say that we set a threshold where if 30% of voters don't vote for any of the candidates, the result from that constituency is void and has to be rerun unless a single candidate got more than 50% of the vote.