If you have a known traveler # and are no longer getting TSA precheck when checking in on the beta website, check the special services: add redress or known traveler number option. Although my number appears in my profile, it was not listed on this screen. After entering the number and rechecking in (did original checkin on classic site and recheckin on beta site) the TSA precheck appeared.

However, for the return flight, the number appeared in the beta website but no TSA precheck. It did not appear when I rechecked in on the classic site. That's what web support told me to do yesterday when I called to ask if something was messed up as I've only not gotten the precheck about 2% of the time prior to about a month ago; no precheck about 40% of the time now. Sigh. No, I'm not calling web support or the Philippines call center again.