All Inhibitors Alive But Towers And Nexus Can Die?

I am the bard in this game and you see that I ult the tower. I was relived when our inhibitor re spawned, knowing that you CANNOT break nexus towers or the nexus if the inhibitors are up. So I looked away and continued playing the game, then all of a sudden I hear "an ally tower has been destroyed" or something like that. I soon realized it was our nexus tower. Now that didn't make sense to me, because all of our inhibitors were up! Then again, the Renekton instantly went for the Nexus, and avoided the inhibitor. Whereas the enemy vayne, not knowing this bug was a thing, targeted the inhibitor, but soon realized that there was no need to attack the inhibitor. Hopefully riot can fix this soon! Thanks for reading and watching this :D