I don't put any stock in the "test" that MSD says to do to check the box. I made this video 6 years ago, I think after the 1st or 2nd failure I had. I was trying to find anything that could be causing the issue I was having at the time.
https://www.youtube.com/watch?v=85PLiA8qIr0Jumping the pickup wires should produce an immediate spark, at least according to MSD. When I did that, I got nothing, repeatedly. That alone should indicate a bad box. But when I went to ANY other ground on the car, it sparked immediately. My box is wired completely independent of everything else on the car, so no external cause could be an issue. The car would not start until I replaced the pickup. Maybe they had a period of faulty production, I don't know, because like JB mentioned above, my last pickup has seemed to be okay for about 3 years now.