Try going back to 1.5.2. and then upgrading to 1.6.0
Maybe worth a try.
It worked for a few others with problems on the update... (It's more of a shot in the dark and it doesn't make sense to me, but maybe worth a try)
I appreciate the suggestion, but I think I'm done jumping through hoops on this beta. Not trying to be snarky. I'll let the developers sort it out.