This happened to me once last year. Of course I didn't realize until I tried using the PreCheck line. Although the BP from the AS App displayed my PreCheck credentials, it would get stripped away when I tried to add to my wallet. Only happened for that flight (subsequent 20ish legs throughout 2021 have been fine) and no matter what tricks I used, PreCheck would not stick when added to the wallet.

The workaround is to just use the BP straight from the App. I submitted feedback to the Alaska Dev team via the app to let them know what was going on. Could very well be an iOS issue though and I could understand that stripped PreCheck from one carriers BP's is not likely a high priority in terms of a software dev backlog.