Moon Base Charlie /Moon Base Delta w/Sims

Oh my...that sinking...you know I tested a world a few months ago that had stuttering in it. WR tested it, too, among the problems for both of us is that we had Ambitions and the world wasn't meant for those with Ambitions. But WR found some sinking landscaping on that world, too. Now I don't know what caused the stuttering and freezes on that world as there were so many minor issues that could have been implicated...or not. But I remember WR cautioning the young lady who built that world about landscape objects sinking on lots with buried portions. Much like WR already mentioning happening with AuntieLynds world that had a lot of underground building.

What does cause that spongy ground? It's almost like the world gets sinkholes.