Had a similar issue with buyer requirements, every time I set it and go back to edit the listing it reverted automatically to the previous setting, problem was fixed by the technical team at ebay, it virtually had to be spelt out to customer service as to what the problem is.

They wrote an email with the explanation, passed it on, and I got a reply email from the guy who took charge and fixed it.

It may take a couple of goes at it in order to get it that far to the right people to look at your problem.