Hi everyone I'm dealing with my first case of sour crop

sobthe hen was acting lethargic with a full crop. This did clear eventually when I brought her in to a cage. I was treating her with miconazole and she was doing great. Empty crop every morning and acting normal all of a sudden the crop just stopped emptying and was filled with fluid. She was like that for 3 days before I had to take her to the vet who emptied the crop for me. She was instantly feeling better once the fluid was gone. I brought her home gave her a tablespoon of mash pellets and I went back to work for 3 hours and her crop was full of fluid again. It didnt seem like she drank a lot of water as I keep a small water container in the cage that hold 250ml and it was barley touched. I ended up in the vet again the next day. And between both vet trips it cost me 500 euro. The vet gave me, antibiotic, anti fungal and a digestive stimulant. I gave her some anti inflammatory aswell and the crop started working again for a couple of days. She was eating well and her crop was empty every morning. Over the weekend the nystatin and antibiotic was finished and I let her out to free range with the rest of the hens for a bit and by Sunday evening her crop was full of fluid and she was looking miserable again.
Any ideas what's going on? Dies the sour crop cause the fluid to sit in the crop or is there an impaction. When her crop isn't full of fluid she seems herself not like any underlying issues going on.
I believe she may have had some grass impacting the crop to begin with and there was a hard ball of grass in one of her poos very compacted together
Did she get more grass stuck over the weekend?
Do I need to put her back on nystatin again? Or at this stage do I need to consider surgery? I was quoted between 300 and 500 for surgery. I by no means can afford it but she is one of the favourite chooks so I don't want to lose her.
Was I just impatient in her recovery? I k ow an impaction causes sour crop but I don't know if sour crop without an impaction can cause fluid yo sit in the crop. There is absolutely nothing solid to be felt in the crop. I'm not sure what I can do