I think Young Mfg. makes bolt carrier groups, not complete uppers. I may be wrong. I'm more interested in what lower you are running? The bolt catch location must be machined precisely and the pin location is critical.
With the lower receiver only and an empty magazine inserted you can examine how the bolt catch mates with the magazine follower to lock the bolt to the rear. With the upper removed and a loaded magazine in place you may be able to identify how it's being levered.
Edited to add: I see you're in California, are you running a bullet button? It may be causing this problem. Custom fitting may be needed to get things operating.