This one will have to go in the Unsolved File.
That chick looks and sounds like a bagpipe.
After most of yesterday and all night with no food and having that crop emptied several times, it was still not completely empty.
When I returned her to her pen she ate like crazy. When I checked just now the crop is massive, far in excess of any food she might have eaten since there was not that much food out there, and there is a ton of air in the crop! Now when I squeeze the crop, food bubbles out her mouth without even having to tip her upside down. It's almost like each exhale of breath is pushed into her crop! ANd she is making odd wheezing sounds, like a bagpipe.
This problem has been going on for quite a while now and is not resolving. While she does not appear to be in pain, she is (in my opinion) slowly starving to death. Wish I had found something succesful or enlightening to share, but this one looks like a loss.