Yo, got the same problem.. We have nice dirt house, just got the first copper tools. Now (shortly after exploring a cave very close to our house that leads directly below our house), our area got instable, which means we cannot live there anymore without loosing it all the time... Any fix for that or is there something we need to destroy? Couldn't explore the whole cave yet as we don't have enough food or sanity for that.. There were a couple smaller ruins we found below, but nothing there seems to be the cause of it.