The Stevens tip-up rifle extractors that I'm familiar with are hinged mechanisms, the lower part screwing into the frame, the two-piece, screwed-together upper part sliding in a slot in the barrels bottom.  They have no springs, no adjustments, and rely on closeness of fit and somewhat on how briskly you break the gun open.  As to why you're having extraction problems, since "30 Schwartz" implies at least a rechambering, it seems probable that in recutting the extractor's profile, its "ears" were shortened, which combined with the extractor's very loose fit causes it to slip under the cartridge's rim.

So how do you fix it?  While it might be possible to build the extractor's top link up with careful welding and refit it, I'd guess it would probably be cheaper and better to have a new link made.  Is Steve Durren or his like in the house?

Bill Lawrence