I bought a used Shield recently, and had to send it into S&W the next day. The striker would stay protruding out of the breech face after a trigger pull, and stay this way while chambering the next round. I am glad that the protruding striker caught the rim of the first round I tried to chamber, or else it may have fired upon seating.

In the notes from S&W, it said that the striker assembly was assembled wrong. I assume this was by the previous owner. S&W replaced it though, so it may have been defective as well.

Overall though, this is why I think they discourage the end user from getting into disassembly of this area.