Hi Russ,
Sorry, I can't answer your question about exactly what (technically) is sent in each of the USB outputs, but I recall that Lee did some experimental work a while back to pass Flarm alerts received from a directly interlinked Flarm Device through to associated Flarm Displays, so that might have a bearing on what you are experiencing. 'Traffic Dynon' and 'Flarm Out' are in effect the same thing. I'm sure Lee will be interested to find out what is going on here. He might well ask you to supply your track file(s) for analysis. Hopefully he will be along shortly and can advise.
Air-to-Air Relay (SkyGRID) works independently of iGRID, so will still work without iGRID (it did before iGRID was introduced), though of course outwith ATOM Ground Station Coverage, your unit will have much less information to relay, so it would be good to resolve the issue rather than simply shut down your iGRID.
I will await Lee's comments with interest.
Best Regards
Peter