Since the parameters are coming through with the asterisks, which you've verified by displaying them in plain text, the only other thing I can think of is that the website or Visual Studio aren't seeing the font correctly. I haven't done any work with bar codes, so I don't have any thoughts about debugging beyond what I've already mentioned.
I suggest creating a new topic in the forum here, titled something like "Barcode Issue" and explain everything there, including the plain text test that you ran to be sure that the asterisks were there. In the forum here, once one of the folks who regularly answers questions here starts working with a topic, the other folks who answer questions frequently will not check that thread so this would be a good way to get attention from someone who has specifically worked with barcodes.
-Dell