When Glocks throw the cases straight back, there are three likely causes. Listed in no particular order.
1. Recoil spring is too heavy. This was a problem when they first started trying to put the double recoil springs on all the guns for commonality. The 9mm guns eventually needed a lighter spring. I don't recall hearing about this being a problem with the larger caliber guns.
2. Weak/improper grip. This can happen with nearly any autopistol if the shooter isn't getting behind the grip enough, but it's more likely the lighter the gun is and the heavier the caliber.
3. Problems with the extractor. If the extractor isn't holding onto the empty properly, ejection can be erratic, with some cases going straight back.