I am alarmed that everyone who has joined the forum recently, has had a complaint about FTE's. This could suggest that some quality control is amiss at S&W.
If I had problems like that my order of priority would be:
1: check the ammo brands...some 15-22's are picky.
2: If happens with every ammo, then check magazines, check to see if they are staggered and angled correctly. Check magazines for defects/dirt.
3: If the mags are fine, make sure the rifle is clean and that there is not a large collection of debris on the breech or feed ramp.
4: The next issue would be with the bolt, possibly the extractor, which I would remove and check that the spring is okay and not either broken or dirty, then add a little oil. Then clean the whole bolt face, extractor, rails.
5:If the problems still persist then I would use my barrel nut tool, to make sure that the barrel nut is tight..loose barrel nuts can cause accuracy issues, seriously loose barrel nuts, I would imagine would cause more serious issues.
Failing after all these checks then I would consider moving the ejector, as the last thing that could cause the issue that would require actual manipulation.
Although to be honest if the issue was FTE every few rounds, then I would take it back to the shop where I bought it or if I were stateside back to Springfield.
I feel for all you guys having issues with your new 15-22's I sincerely hope you get them sorted out so you can get to actually shooting the rifle and enjoying it.