As a gunsmith with 40 years of experience, I can answer this pretty well.
In all my life I have had to repair 2 "controlled feed" extractors and both were victim of work done wrong. One was over-ground on a Mauser that a man was converting to a belted magnum out of a standard extractor. It needed to be replaced.
The other was also on a Mauser that a man had ground the face down thinner on (I have no idea why) He's heated it to a point it was soft. Other than fixing “bubbaed” work, I have never had to fix one. Not one!
Now if I look at push feed rifles I have had come into my shop for repairs I can say that in my old shop which was open to the public (not my current work shop) and in the places of business that I used to do gunsmithing for I have had probably 200-300 rifles in need of repair. Most have been nothing more than the ejector getting stuck in the hole due to lack of cleaning. Notable among those was the older "Post 64" M-70 Winchesters and Savage 110 actions. Also a few Remingtons.
With Remingtons the main problem I have had to deal with is breaking extractors.
Better for the ejector to stick than the extractor to break.
When the ejector sticks the gun will work, but you need to shake out the empty, or in some cases flick it out with a finger. It will withdraw the shell but not throw it away.
In the case of the extractor breaking as I have seen in Remington 721, 722 and 700s the gun is out of commission 100% until you can get a rod down the barrel to knock out the old shell. Even then you would have the option of firing 1 shot only between "rod knocks". At least with a stuck ejector you have a workable rifle. It will take 2-3 seconds between shots to get the brass out, but that's better than having to run a rod down the bore.
I have seen the extractors break in their “T” slots a few times on Savage 110 actions and also 2 times on Mossburgs and 2 times on Howas. These failures leave the brass in the chamber too. So the “rod assisted reload” is what needs to happen if and when those extractors break.
I know a man and his son in Nevada that had that exact thing happen to them on a deer hunt, and they used a piece of rod to drop down the bore and knock out the shell rather than go home. To their credit they were both good shots, and they both killed their deer with the broken Remington 700 . “We told ourselves just don’t miss and it will be fine” is what the man told me when he brought in the rifle for me to fix. His kid said he felt like Daniel Boone reloading his 30-06. We all had a laugh over that.
For those that have push feed rifles, I am NOT telling you to dump them and get a controlled feed rifle. They are usually fine, but they do need attention.
Here’s what you do;
When you clean your rifle always dip the bolt head into the solvent and wipe away the drips, but leave it a bit damp. Leave it that way. I recommend the old Hoppies #9 because it doesn’t rust steel at all. Store the gun with a damp bolt head. When you get out the rifle to go shoot, dry it out a bit with a tissue and have fun.
The solvent floats and dissolves the bits of junk that get built up in the bolt extractor and ejector recesses over time. You store the gun far more than you fire the gun. So in the storage time the solvent does it’s work and you just stay ahead of the build up buy wetting he bolt face. If you do this with your rifles you will probably go your whole life and never have a problem.
If you use a “copper solvent” wet your bolt face and let it stand for about 30 minutes. Then wash it out with hot water and dish detergent and blow it dry, then oil it. The ammonia based aggressive copper solvents will often rust steel if left over long periods of time. So get rid of the ammonia with a water flush so the springs and parts don’t develop rust pits where you can’t see them, which can also lead to parts failure.
If you’d like, it also may be a good idea to spend a few bucks to just buy an extra extractor, ejector and springs, ball bearings and so on. Keep them in a pill bottle in your kit “just in case” Very cheep insurance.