If I prepared the "antitussive and decongestant syrup" as given on the Dynaphar site I always get a neeslag, presumably of sorbic acid. What is this due to?

I suspect that the prescribed method of preparation is not the ideal. Therefore, try this method for the preparation of 200 ml syrup:

weigh the individual ingredients.

Pour 10 g of purified water into a recipi ë NT (1); Heat lightly to 400mg codeine phosphate; 1.2 g pseudoephedrine and 200 mg citric acid to dissolve. Add 10g strong orange peel tincture and part of the sorbitol solution. Mix.

dissolve in a second Recipi ë NT (2) 300mg potassium sorbate in 10g purified water and add 50 g sorbitol solution.

then add (2) to (1) and mix.

pour (1) into a tarred bottle and rinse with 50 g sorbitol syrup. Add (2) and rinse with 50 g sorbitol syrup. Mix and apply weight (up to 246 g) with the remaining sorbitol solution.

Apply the green label NR2 (do not exceed the indicated quantity).