I have been trouble shooting a 29-2 that has a similar problem. After reading the responses to your post I decided to look at the counter bore. It turns out I have one chamber (opposite to the ones I thought were giving me trouble) where the round has to be snapped into position for just the rim. To get it out I had to forcibly pop it out with the extractor. After doing that several times it smooths out. Examined the case and there was a mark where something was rubbing on it. It was caused by a burr just at the star. Took a small round file and got rid of the burr and the round slides in smoothly all the way in and extracts easily. Now to the range to see if the cylinder still jams up.

I think everyone is correct that you should look at the counter bore and the chamber near it. Good luck, and I'll have a range report soon.