Take it out and shoot it. If it doesn't throw brass at your face, there is no problem. If it does do it consistently with a cross section of loadings (unlikely but possible), return it to Glock for adjustment. I have had one since 1998 with bushels of rounds through it and it has never thrown brass at my face that I can recall.I heard about brass to the face issues ...
I bought Gen 3 G19 in September, test date was April or May of 2011. It has the 336 ejector. I have run 650 rounds through it so far. I have never had a problem with ejection. 2 weeks ago though I let my dad shoot a magazine through it and it threw 2 or 3 right back toward his face, he didn't notice or care. At the same time I noticed he doesn't lock either one of his arms when shooting and both of them are really bent at the elbows. My guess is his loose arms, versus my shooting arm being locked straight has some sort of effect on the difference in ejection. All of my empties seem to eject right into the screen on my right side and drop down to the shooting table.
My Gen 3 G19 left the factory in 8/10 and has a 336 extractor. No issues at all. It seems like there are more extractor issues these days than in the past but I do not think it is as wide spread as some are making it.
I think you mean ejector.
BTW, Gen 4 G19, 0-4-3 guide rod, 336 ejector = 0 problems of any kind.