Thank you for that information. I don’t see anything that stands out in the logs, but there were a couple issues related to AD User Sources that have been fixed since beta 2, so it’s possible you were running into one of those.
If you do run into the same issue after performing a restore onto RC1, then I’d like to get a gwbk from you to try to replicate. Just let me know, and I can send you a link to upload it.