Our home is 2 years old. The problem I am having is with the red wood railing around the deck. Most of the sapping has stopped but the paint is still chipping. I am using Sherwin Williams quick seal 350 hs alkyd stain blocker primer which is supposed to block knots/sap. Top coat is Behr exterior flat prem/plus 100% latex. For the 3rd time I primed and painted this railing. It almost seems like I’m getting new sap bleeds thru the paint. I live in N. California and are located about 300 yards from the American river which gives us damp am mornings. Any suggestion?