Originally Posted by
WDR
It appears that you might be lubricating the striker assembly... if you are, stop. It should be dry. As should the channel its riding in. Not sure if that is your issue, but I have heard of lube catching junk and or (with excessive amounts) slowing down the striker enough to cause issues. In any event, the first thing I'd do is make sure the striker channel and striker and clean and dry. If that didn't help, and the striker itself looked okay, I might try a new set of spring cups (cheap, and I always have some on hand). Channel liner and the sleeve on the rear of the striker maybe too.
With the slide assembled and the safety plunger depressed, how much of the tip of the striker is sticking out proud of the breech face when you push it forward?
I have never had hard primer issues with Winchester ammo... but it's possible things have changed. I'd be inclined to try a different brand just to see what happens. If it happens with another brand of ammo, it might be time to send it back to Glock and have them look at it.