^^^ that is normal. It takes a while to compute the stability and decide to fall even on a fast computer, so you have to wait it out.

I don't know what changed, some little something was just that much, but you need to get support back on it. The easiest way if you didn't use iron at all is to do so now, embed a wood-iron pole in the ground inside the walls and go up about 3-4 poles and it should stretch the support upwards enough to fix the issue. This would be on the walls that support that roof area.