Went out Tuesday evening and noticed that the primer over an area of filler had puckered and cracked. Not good. Attacked the area with a sander and it became obvious that the filler was some from a badly mixed batch I had applied years ago. It had never cured and was still soft and had caused the problem. I was able to use the sander and a scraper to remove all the bad filler. I then mixed up a good batch of filler and applied it.