And you can get a leak into the hull at the cockpit drain if the adhesive stuff that holds the cockpit to the hull (inside the hull) comes loose. The hull then can move relative to the cockpit, making any sealant placed there ineffective. If you have taken the brass fitting apart you should be able to check for leaks in that area. There are threads devoted to how to fix this. You generally need to install access ports in the back of the cockpit. I'd hope for a leak that's easier to repair, like the missing 0-ring shown above!