Pulling over at Makati Medical Center, I tried changing wheels and used my spare. The problem didn't go away, however. Dropping off Mav at her office, I drove to Pitworkz Hongly in Sucat.
There the problem became apparent. The lower control arm that I had them replace last Saturday wasn't as securely bolted on as it should have been, and had come loose. A once-over with an impact wrench later and it was back to normal. Without any trailing cars, I sped up and braked hard a few times along Sucat Road, and Aibo's surefooted braking stability was back.
Whew. I'm just grateful nothing worse happened.