Fact is normal closing of just about any semi-auto .22 could result in a slam fire. Normally it is extremely rare in a properly set up .22 semiauto and most people will never experience one. I had it happen once in a ruger 10-22 rifle that I use to regularly fire 500 rounds on a weekly basis. When ever chambering a round in any .22 it is even more imperative then for a centerfire that it not be pointing at anything that you do not want to shoot. Any out of spec cartridge that is too thick, a little fragment of dirt or what ever between the rim and the bolt or chamber could exert pressure on that thin ring of priming material on the inside of that rim. Usually 99,999 times of out one 100,000 bolt closings nothing will happen. (I do not not have a scientific study for that figure)
Debris in the bolt crossed my mind as only 2 reported issues with thousands of firearms seems like a needle in the haystack, unless Ruger actually looked at the bolts and found them out of spec. which is probably the case. I've never experienced a slam fire, but i know it happens so like most people I have the firearm pointed in a safe direction when the bolt slams home.
The inspection tool is free from Smith & Wesson. Just enter the serial number and they send it to you free. I ordered one for myself and one for the grandson's rifle.