Most recently...

Intermittent creaking noises turned out to be the padded comfort saddle rather than the bottom bracket. Yeah, the BB wobbles a bit, but it's not making those noises. I'd never had a creaky saddle before and didn't think to check the most obvious solution. I could only hear the noises were coming from somewhere below and assumed the worst.

And a frame mounted video camera was picking up noises amplified by the aluminum tubes. With the unaided ear I couldn't hear the stuff the camera was picking up when mounted on the head tube. So I moved the camera to the handlebars. Problem solved.