Don't fix what ain't broke. Clean the area around the extractor hook and examine the extractor closely to determine if it is bad; if it looks OK, try other ammo.
Not a bad thought.
If the extractor hook is clean and dry, and doesn't have any chips or a broken edge, it might be the ammunition (case rim tolerance), or, depending on the age and amount of usage the gun has received the extractor spring might be weakening.
How old is the recoil spring?A damaged or weak recoil spring can be involved with some failures-to-extract, too. FWIW, the factory recommendation to armorers is to replace the recoil spring (and mag springs) either every 5 years (of service use) or every 5,000 rounds fired, whichever occurs first.
In LE guns that are left with a round in chamber all the time (compressing the extractor spring) it's not unusual to see them start to exhibit weakening after something like 10 years or 10,000 rounds, meaning after a fairly long service life. I started to notice chipped/broken extractors and/or weakened extractor springs in our aging inventory of very early production 3rd gen S&W pistols as they reached the 12-16 year point in service.
Replacing the extractor is a job for either the factory, a S&W armorer or a gunsmith familiar with S&W pistols.
The extractors typically require fitting in the way of filing on an adjustment pad located behind the hook, which is what controls how far the hook reaches inward and engages the case rim. A Go/No-Go bar gauge tool is used to determine when the proper adjustment has been reached by measuring the distance between the extractor hook and the opposite breech face shoulder.
Back several years ago S&W armorers also used a flag gauge which checked for the dimension under the extractor hook to the breech face, but newer machining methods on later production guns and newer extractors have eliminated the need for it and this tool is no longer sold to armorers in tool kits.
The extractor spring tension is checked with a force dial gauge, and there's some variance of the recommended tension range depending on whether the pistol has the older rounded breech face machining or the newer straight cut breech face.
Also, sometimes an older 3rd gen model may require one or the other of the revised repair extractor springs in order to get the tension in the best range for feeding & extraction in the older model guns.
Getting the extractor pins out of the older guns can be a bit daunting, as they usually require some force to break them free and get them moving. We're talking a 4 oz ball peen hammer and a starter punch. Once free to move, the pins can be removed using a straight shank 1/16" pin punch, keeping the extractor compressed a bit to avoid bending the pin punch. (Bending the 1/16" pin punches is also a good way to create a new 'starter punch' when the punch is broken off at the base where the taper starts, and armorers can sometimes end up with a couple or more 'starter punches' because of bent pin punches.
) They're removed out the bottom of the slide and are reinstalled from the bottom. In older models armorers were given tapered needle reamers to clean out the slide's pin hole (taking care not to enlarge the pin hole).
Not really a kitchen table gunsmithing project for someone without the right tools and preferably some experience.
Just some thoughts.