RedSquare - IMHO you should skip that advice about smoothing your nib. I suspect the problem is just that your pen runs too dry. Odds are high the tines on your nib are touching very tightly. It's OK for a soft nib's tines to touch because they should spread a little with minor pressure... the problem is -- the 3776 Century's tine cut is not very deep so the tines don't really spread much with pressure.
Therefore if the tines are touching tightly then when you apply pressure they won't open much or at all - and therefore ink won't flow.
With no ink flow your pen will feel scratchy even if the tipping is fine.
Yes, check alignment first, of course... but the issue I'm talking about is probably the problem. I have owned three Platinum soft nibs with this issue that came from the factory completely unusable. (No, not user error. I mean literally not usable.)
If I'm correct in my diagnosis - reducing the tension in your tines or even allowing a super ultra narrow gap - will get your pen flowing well.
Check out this photo: https://imgur.com/gallery/owGN5mZ
That's a firm nib, so you don't necessarily need that gap for your soft nib. But that gets to the heart of what is probably the issue -- if the tines are too tight the ink is not going to flow.
As far as the feed channel not being deep enough as someone suggested -- that is almost certainly NOT the issue as the feeds are mass produced with consistency. This issue of tine gap and tightness-of-tines, however, is not consistent.
Anyhow, correcting this issue is probably too much for someone at your level - and you don't want to 'learn' on an expensive nib. I would send it to someone like Mark Bacas at nibgrinder.com for adjustment... or any of the popular nibmeisters. I just have experience with him so he's who I tend to recommend.
I wouldn't return it because there's a good chance the replacement would have the same issue. I would just have a nibmeister adjust it and then it will be perfect. Good luck.