That was the same for me. From the beginning, I had PC, and only missed once in over 100 flights, up until a couple weeks ago when - WHAM - suddenly I didn't get the Pre-Check signal on my BP anymore and I had to go through regular security. This happened six or eight flights in a row. After forcing the issue with DL, they re-entered my name and now I'm back to always getting PC. It seems that is what has happened to the OP, too. There appears to be something in the DL system that we cannot see that changes. Having them go back in a re-enter the name seems to correct this mystery problem. Even now that it's switched back to the way the name was to begin with, I'm still getting PC.