Ok, swinging back. After talking to a few people, I was convinced to check the hanger....I talked myself into adding to my tool chest. The Park DAG-3 arrived yesterday, and guess what? The hanger was indeed bent. At the probe end, I'd estimate it was out about 10-12mm. So I bent it back. It was quite easy. I reindexed the gears, and I'll check it out on my ride tomorrow. It occurs to me that this might not solve the problem, but at least I am narrowing the possibilities as I go.