I have an issue with a ceiling that I have never come across before. I scraped the popcorn off the ceiling, fix some imperfections, sprayed a knockdown and painted it with white, flat ceiling paint. Every joint flashed through. No problem, seen it before and used a oil blocker over the entire ceiling. Painted it again and it flashed again; butt joint, screw holes, etc. I'm at a loss. What do I do?