Is there some sort of subcooler that actually reduces liquid temperature below the evap temperature on this thing? Economized screw?

That is a pretty descriptive frost pattern on the suction header in one of those photos...Appears like three tubes are getting all the liquid. In the meantime the frost is all the way back to the outlet stub on the TXV...

Somebody mentioned orifice plate...I've seen TXV's this way just a few times. One TXV was receiving Min 15 deg upstream liquid and trying to maintain a 9-deg room on a 0-deg EPR setting. TXV head was much colder than the suction and all the charge was lying right on top of the diaphragm. No Feed.

Other one had no orifice plate in the distributor but that did not cause funny distribution....just a lot of frost on the cap tubes.

Third one had a collection of tubes crushed due to ice bridging at the pan; that never cleared during the defrost. Didn't pass much gas during the defrost either.

This unit have a hot gas header? Does it use hot gas in its pan?