Quoted:
90% of the time the spent case will not make it out of the gun and gets jammed along with the new round.
I'll put money on the problem being your ejector. There is a
tiny space that the face of the ejector needs to be in for it to properly work. If it doesn't, the fresh round is what strips the empty off the bolt face, causing exactly the problem you describe.
The ejector needs to be almost in contact with the ejector channel in the bolt. Try to
very gently bend the whole ejector inward, toward the centerline of the weapon, and then see if the gun will eject an empty case. Keep trying with small adjustments until you run the ejector into the bolt, then back off the tiniest amount.
In rare cases, the face of the ejector is not lined up with the bolt face, and you can see "partial ejection" and other problems, But it sounds like your problem is just that the ejector isn't quite located perfectly, and that's a problem you can fix in a few minutes at your workbench with a handful of empty cases and careful tweaking. For what it's worth, this applies to any Colt-style 9mm carbine, whether you're using a standard lower receiver with a magazine block or a dedicated 9mm lower.