Fixed. See attached build.

Yep that got it, I noticed there is no longer a derived table so for the hell of it I changed the first line to var oc = MetaData.OcOccurrence.AsQueryable().Select(x=>x); which resulted in a derived table with an alias SQL error. Don't know if you care - I certainly don't.

Hmm... I'll see if I can repro that one.

Fixed. It's not as edge case as you might expect. Fixed in next build. I think you'll run into it eventually, so it was fixed. it's not that strange, the code wasn't doing things that cleverly when determining an alias for a side of a join.