It could just be that it's an EF nib.
I have an EF nib on one of my 51 Vacs and when I had it restored I found it seemed a bit scratchy, so I had the the repair person (Ron Zorn) open up the tines a little bit for me. That helped *immensely* (I'm not fond of EF nibs normally, but I found the pen in the wild for a good price -- $25 and it has a 1/10 16K gold-filled cap).
Once the flow got increased a bit, with the opening up of the tines, it became a very solid writer -- very good for when I have to take copious notes.
I agree that you should contact the seller and explain the situation. It might be as simple a solution as that, and if you're not comfortable in doing it yourself, see it the seller can do it for you.
Ruth Morrisson aka inkstainedruth
"It's very nice, but frankly, when I signed that list for a P-51, what I had in mind was a fountain pen."