If the lower cost options do not work, you wold likely get a lot better performance form a high temp amorphous resins IE PEI (Ultem) Polysulfone or PES, type product. there are food grades available and all the amber colored food service trays (McDonalds, etc) I think are these type of products.
Processing issue swill be difficult to fix without addressing the problem, like insufficient drying. You could also look at another DuPont product like ST801AW BK (super tough and weatherable) This might help with durability.
