Pockmarked texture on painted interior wall
I am in the process of repainting the interior walls in one of the bedrooms in our home. The walls are drywall, and paint is a flat latex Behr, in the same color I painted the walls about 12 years ago. I've been rolling the paint with a Purdy 3/8" nap roller, and a good frame.
On the biggest wall in the room, I am having a very frustrating problem where a pockmark texture is appearing in certain areas. It looks somewhat like the surface of the moon. This isn't particularly visible from straight on, but when the wall is viewed from an angle, especially in the morning light, it's quite obvious.
In an attempt to fix the problem, I have repainted the wall numerous times using different techniques (the W/M pattern, rolling the entire height of the wall, etc.), and have even primed the wall and repainted it. Nothing has helped.
Can anyone explain to me what's causing this effect, and how I can fix it?