Samantha has discovered that the ceiling in the guest room is one coat of water-based paint on top of raw plaster. Idiots. The people who have owned this house before us are idiots.
Add that to the "very small" water problem in the basement "only during the heaviest rains". Try a flowing stream whenever more than 20 minutes of rain falls.
In British Columbia, the sellers would be considered in breach of contract for not making a full-disclosure about the condition of the house. Obviously in the US, it is always caveat emptor.