Toyota - Corolla :: Noise Coming From The Rear Of Car And Tire Cupping

I've had some noise while doing slow turns for the past 9 months or so, seemingly coming from the rear of the car. It's sort of a rrrrr ----rrrrrr -rrrrr noise, but it has a slight buzz to it too, like something is vibrating. It's hard to say which side it is coming from. It only occurs when turning to the right. But recently it sometimes occurs when going straight, but slow, like when approaching a stop light. Braking seems to have no effect. The other symptom is the left rear tire has very definite cupping. There are easy to see flat spots on the surface of the tire. The tire isn't perfectly round in other words, but more like an alternating sequence of flat spots. The other 3 tires don't have this cupping, they show a normal wear pattern.

I jacked up the rear of the car and tested each tire to see if I could detect anything wrong. I pulled, pushed, twisted. I could detect no play at all in either tire. I spun the tires by hand, and there was no unusual noise. They both just spun quietly, freely, with no apparent wobble or anything unusual. The service manual says the rear wheel bearing is bad if there is 0.2 mm of axial play. I doubt I could have detected 0.2 mm of play the way I did it, just pulling on the tire.

The only other thing I noticed is that the (rear) toe-in adjustment is different on the left than on the left. By this I mean the eccentric bolt-gadget is set on different marks on each side. The right one looks like it is set to have more toe in that the left. The right one is 4 marks positive toe-in, the left is 1 marks positive toe-in. I'm assuming these marks are just for reference, and don't represent the actual toe-in, just that's the setting it took to get the rear wheel alignment correct when the car was built.

Do I have a rear wheel bearing problem? A rear-tire alignment problem? Something else?