There are good and less good fingerboards on the Stagg EUBs. I got two (cheap via Ebay because they were slightly damaged), one of them with a good fingerboard, one of them less good. But it could also be a defective string (i.e. getting a bit thicker than it should).
If it is only a very little bit of buzzing and you are sure it is the fingerboard and not the string, you might be able to scrape off a little bit of the fingerboard finish just below the position where your left hand finger is when it buzzes. But be very very careful and don't remove too much (thickness and length) or you will ruin your fingerboard.
I once did it myself on my bass because the luthier did what he could and it took me about two months, working just a very little bit every few days on the fingerboard (under just this one string) until the buzzes got away. Usually this is a job for a luthier, but too expensive to pay.
I won't try to polish the Fingerboard after the final scraping, at least not too much.
Well, like I said, there's no buzzing as it is, and I find the action very playable, so there won't be any need to do any work on the fingerboard. Thanks for the info, though.