I'm new to this board and new to gun shooting in general. I just purchased a Glock 19 gen 4 and am having the same malfunctions you described which is most frustrating to a newbie. I picked Glock for their reputation as reliable but for now that is not the case.
I was beginning to think it was me, but not anymore. You'd think it could have been caught when testing the models given the numbers of people complaining about the issue.
Actually a lot of U.S 9x19 ammo is weaker than Euro 9x19. The Glock is designed for full power ammo. Hence its reputation for a long life.
The recoil springs should have been a U.S part with the U.S avg 9x19 round considered. Possibly some bean counter got into the mix.
Glock will make it right. To bad they have to though.