Has anyone been having issues with KTNs not being applied to reservations with DL lately?

Traveling with my father a little over a month ago, he somehow didn't receive PreCheck despite my ensuring it was applied to his reservation at booking (I made the booking myself).

Now two days ago leaving GSP I also failed to receive PreCheck, again, despite my ensuring my KTN was applied at booking. I haven't had this issue on AA or any other airlines at the moment, seems to be something related to the Delta system. TSA officer at GSP was very understanding and said I could go back down to the TA to have them enter it into my reservation and reprint my boarding passes but since I was literally the only person in line for 'regular' security I just did that. I sort of regretted that decision after remembering how much crap you have to pull out of your bag to run through the X-Ray.