This is what can happen when you paint your place in a really dark colour.
Because of the sun and possibly still very green timber. As soon as the hot weather kicks in everything heats up And this is what can happen.
Old boards also have a tendency to bubble in some spots where it gets a lot of direct sunlight or heavy sun.
This is very hard to detect when starting a project. Even with a lot of preparation. Best solution is to rip it back to bare timber and start the prep again.
Finshed results amazing 👍🏼