Nexus blitz bug. Nexus unattackable

I was playing a game with draven. We reached the point where it was a sudden death. Our walking nexus spawned but their didn't. When we came to their nexus, it was unattackable. Because many people point the blame to ezreal, both teams didn't have ezreal. Our skarner said it was bugged because of his ult but idk. Might be a coding bug since their walking nexus didn't spawn.