I have a customer with some old cedar siding that is suffering some peeling issues. She has recently put an addition on the house with new cedar and after letting it age she has primed it and some of the existing cedar with a good oil based primer and coated over it all with a waterborne house paint. However both the new and old siding has paint peeling where the end joints of the wood butt together. This is clapboard siding I believe. Normally I'd suspect a moisture issues but the inside of the house is undergoing renovation so all the drywall is torn out and the back of the siding is completely exposed to heat and airflow. There is no apparent moisture on the inside of the siding. This peeling occurs just a couple months after painting. I'm thinking of thinning a good oil primer down with penetrol for deep penetration and telling her to coat over it with a good flexible acrylic, but this is so similar to what she has already done that I'm afraid she'll run into the same issue. Any input would be appreciated.