Chain Pops When Leaving Cogs
If I understand the description of the issue properly: the chain hangs on the cassette sprockets slightly at the approx. 12 o'clock position where it should be peeling off to go to the chainrings, then 'pops' as it lets go.

In other words, you have slight chainsuck on some teeth of some cassette sprockets.

If there is a slight manufacturing defects or burrs on some cassette sprocket teeth that is catching the chain, those are probably going to wear off pretty quickly. I'd try to put a few miles on the bike and see if the problem resolves itself.

Something else you should probably check for are stiff joints between links in the chain. Again, some running-in wear on the drivetrain may resolve chain problems.