...or your house quit moving around.
No, the house has a gutter between the first and second floor on the back. The previous owners never cleaned the gutters out the last four years they lived there(there was four layers of debris in them when I cleaned them out).
They went to Florida during the winter the last two years.
The water, ice in that gutter backed up and got between the first and second floor of the house. Staining and cracking the ceiling in the kitchen/family room.
This house as I stated was built in 1972. During the Saudi Oil embargo. So, it was originally built with electric radiant heating wires in the ceiling. They attached blue board to the ceiling joists. Stapled these 18 gauge wirde to the blue board and then covered it with about 1/4-3/8” of plaster.
I actually hired a plaster expert to help me for a couple days repairing that ceiling. We removed about a 8x10 section because it was sagging. During that I also installed recessed LED can lights in the kitchen ceiling. Moved the box for a light over the kitchen table. Then we fixed cracks and remudded with regular drywall mud. We also replaced the insulation along the back of the house that got wet.
It still looks perfect today.