One of mine had the same issue with extracting the empty casings, for $10 I would change out the extractor and try a new/different mag first. After 13 years you could have a bad magazine.
The cheapest thing to try is remove the bolt take a good look around the extractor and see if there is "gunk" (technical term) around it. If so soak it for a few minutes in the cleanser of your choice and scrub it with a toothbrush. Re-assemble and see if that fixes the problem.
If not, replace the extractor with the Volquartsen Edge Extractor mentioned above it takes all of 5 minutes and is really easy to do.
I would go with the extractor as well, though I've not had a problem with mine (yet). I use 25 rd mags for target shooting and the Ruger 10 rd mags when squirrel/rabbit hunting.