Buildings disappearing

Game mode: Singleplayer
Problem: Bug/Performance

So, I convinced my friend to buy this game on PS4, as I was hooked on the PC version but he doesn’t have a pc. He and I played for a week and the game slowly grew on him. I built a medium sized round colisseum-style building and he had built a fairly large 3 story architectural masterpiece. He finished it, and stepped away to see how it looked lit up in the dark and it fell. All of it. Just gone. As well as my structure. Building decay was turned off. WTF … now he’s done with the game and I may be too.