I've had major ejection problems with my two gen 4 G21s.
And at the same time no problems whatsoever with my two gen 3 21's.
Hope yours is a better copy.
I even sent one of the new 21's to Glock and they admitted there was some big problem with it and sent me a new one. Unfortunately.......it had the exact same problem.
At this point I didn't feel like sending the other one back.
Just decided to live with the brass in face and weak ejections.
It is a problem though when running to the right while shooting.
Again, I hop you will have better luck with yours.