
Let's breath some new life into this one!
Don't forget that there's also a generation 2.5 Glock. (That would be a 2nd generation frame with finger grooves.) These changes are often more than just cosmetic; the problem is that Glock doesn't often announce internal changes. (Think, 'lock blocks' on 3rd generation G-22's.)
The #4256-1 trigger bar change on: G-20's, 21's, and 30's wasn't announced by the factory; it was just repeatedly posted on Glock Talk; and, after awhile, everyone caught on. I suspect the troublesome G-36 has had either its magazines or frame quietly modified; but, there's no way I can prove this suspicion. I know the new G-21SF has a different slide and barrel configuration; but, this is because someone on Glock Talk took the time to actually measure these differences. As usual the factory has, yet, to say a word.
Light strikes? It's not common knowledge that Glock trigger bars have been regularly manufactured with 3 different, 'bird's head' configurations. (The trigger bars are, like the springs, contract-supplied parts.) If the bird's head at the tail of the trigger bar is just slightly off (too short) the pistol may deliver an occasional light strike. Extra power striker springs work fine; I have them in both my EDC Glocks. The combination you want to AVOID is an extra power (Wolff) firing pin spring, AND a reduced power recoil spring - That could, definitely, cause your Glock to fire OOB.
OOB events are often signaled by either light or off-center primer strikes. It's been my experience that many times you'll feel the slide chattering OOB as it cycles - especially during rapid fire. Fortunately, if your Glock is a 3rd generation pistol and properly set up, an OOB event is exceedingly rare.
I have an entirely different take on Glock kaBoom! events; I don't think they're all caused by the slide being out-of-battery; instead, I believe many Glock kaBooms! are caused by trigger bar and double fire problems. (No, I don't feel like arguing the question. Let's just say that I'm not enamored by Glock's so-called, 'drop safety' - Which isn't the kind of, 'drop safety' that most people think that it is!)