Older world generated before. Older than 0.13.0. Beyond that I can't be certain when. Already marked off two spots containing an invisible chest in this nether fortress I just found.
Still occurring in 0.14.0. Encountered exactly as described in nether fortress.
I didn't write this ticket. It was already here and wasn't marked as duplicate. I did search and this is what came up. All I did was add a comment.