I say , when in doubt consult a vet, here is some advise on impacted crop but not on sour crop. I personally couldnt bring myself to use super glue I would let a vet do it but for interest of how some people treat this:
Treating Impacted or Bound Crop in Chickens
If you suspect your chicken has an impacted crop start treatment in the morning by dropping a small amount of olive oil or liquid paraffin (2-3ml) into the birds mouth and then gently massaging the crop to help break up the compaction and repeat this procedure in the afternoon.
Feed a soft food such as layers mash and again add some natural yoghurt to soften the food and neutralise and bacterial build up in the crop.
It may take a couple of days to break up the compaction, but if it persists for three days the compaction may need surgically removing. If you are not confident carrying this out yourself take the bird straight to the vets where they can perform the operation.
In the event you wish to carry this out operation yourself you will need a scalpel, rubbing alcohol, cotton wool, clean towels, water, saline solution (at blood temperature), an additional pair of hands to hold the bird securely and superglue.
Firstly wrap the chicken in a towel and hold securely. Next, locate the chickens crop and sterilise with the alcohol and then make an incision about half way down the crop of about 1cm using enough pressure to cut through the skin and the thin muscle area below.
Once the incision is made quickly remove the contents of the crop and then rinse the crop with the saline solution. Put a thin line of superglue along the incision and hold the edges of the muscle and skin together so they seal. Superglue was actually invented as a method of treating injuries on the battlefield for the US Army.
Clean the exterior area and again rub with the alcohol solution. Isolate the chicken in a clean secure coop and do not give any food or water for at least 18 hours. After this provide water and small amounts of liquefied food such as pureed fruit or mash.
If you suspect infection go straight to the vet for further treatment. Always seek the advice of a vet if the condition worsens.