Sounds like the roof might be the problem, and not the paint! If it is a new sale than I suggest you get someone in quick to take a look. You may want to go back to the previous owners and confront them with the find. It could also be cracking from the settling it has been doing for the past 56 years.

Now define cottage. Is it a 4 season residence, or is it a vacation spot used 3 seasons a year? Is there snow in the winter? If so, one thing that people forget when painting in a 3 season cottage is that interior paint is not appropriate! Interior paint is made for temperatures that don't fluctuate much. Exterior paint is designed to withstand rain, wind, sun, snow, warming, thawing etc. It could be that over the years the interior paint components have simply broken down and are no longer able to withstand the environment.

We live in the home year-round, and we are in the deep south so snow/cold climate isn't the problem. The roof didn't have any leaks when we moved in, or at least not according to the home inspection. Before we moved in, however, the home had been vacant for several (two or three???) years and was exposed to the high moisture and heat of the area. Perhaps the fluxuating temps due to the home being vacant is the problem? My main concern is how to remedy the problem. I've tried scraping, but more peels off in pieces the size of my hand a few days later. It seems impossible to peel it all away. I'm considering a chemical paint stripper of some sort... think this is the way to go?