Was having that happen with a cauldron on a hearth until I demolished the hearth, replaced it and then positioned the cauldron again.

Try rotating em.

I only recently ran into this kind of thing. I believe it is stability; it turns out that everything requires stability. I had a table in the middle of a large room with wood floors with minimal support, so the table had actually gone red in terms of what it could hold. I was sticking a chest on top of it and after a while the chest would explode - it takes a few moments all the way to many seconds for the game to compute stability and decide to blow something up. I put some support below and it was fine, though that was not really what I wanted so I ended up moving the table a few tiles toward the edge instead.