appreciate your input, thanks. A fellow shooter said he's got 1911 springs I could try. Wolff springs aren't a stock item in Finnish gunshops, unfortunately, otherwise I'd have bought spares already. I'll mail order a few anyways. I don't think I'll need the lighter springs you mention because I only use this gun for IPSC with loads that make major, it's not exactly a bullseye gun. There is a slide buffer on the gun.
The reason I think the spring is faulty is that I can't see anything wrong with anything else, maybe I'm just dumb(?). I'll go shooting tomorrow and see what happens with the new spring & post the news.