I have used literally thousands of S&B primers. Without issue. Until recently. I installed a Zev trigger kit in my Glock 21. I started getting FTF's with the S&G LP primers. A lot of them. I realize that it is a lighter trigger so taking that into account I started using CCI LP primers. They ignite without issue, zero FTF's with them. I also started having issues in my STI 45 with the S&B primers. Using the CCI LP primers dealt with that issue as well. I hadn't used the S&B primers in that pistol until recently. However, i use the S&B LP primers in my JR carbine and my son's without issues.
I also use the S&B small pistol primers in a number of 9mm's and have never had an issue with them.
So I have come to the conclusion that some pistols with a lighter trigger may not ignite consistently with the S&B primers, specifically LP primers for me anyway.