I'm not sure why its not emptying completely. I do have a 7yo rooster who's crop does not empty all the way when I check it in the morning, I don't know why, it could be old age. He does not act lethargic at all and is completely normal, he is going through a little molt now. A couple weeks ago I was holding him and his crop was full and I accidently pushed stuff up and he aspirated, I thought he was going to die, he was making a bunch of weird noises and had labored breathing. He got better and I started treating him for sour crop, his crop would almost never empty it would be small though, I was using the same treatment as you. I stopped treating him for it because I didn't think he had sour crop, his breath never smelled. His crop never empties fully when I check him in the morning but he's not acting sick so I'm not to worried about it. Its strange, I would think this would eventually lead to sour crop, right? If someone could shed some light on that I would appreciate it.