So, while I thought for a little while that blowing in the connection and clearing out worked, I was wrong. BUT I switched to a new adapter of three that I have, and found the problem is MUCH diminished. The TNP adapter I was using died, the LAN port stopped working. So now I am using another off-brand from a company called Juiced, I can't recommend it, think its luck of the draw really, and maybe another copy of the TNP would be good... YMMV i.e., but its working for me.
I wonder if we are all discussing similar problems with more than one root cause. Heres why I say that:
1) Rebooting has NO impact on my screen sheering/flicker, comes back immediately on restart
2) My screen sheers unusably with 1 adapter, was workable with the TNP, and is much improved with the latest adapter I am using
3) I found with the TNP adapter that if I flipped the usb male side around, I got much better performance. While USB C should be non-directional, in practice, this wasn't the case for me and inserting the adapter one way up was better than the other significantly, reliably and noticeably.
4) If my screen starts to sheer, shake or flicker, I find that if I flip the male plug around I can usually stop it. Reconnecting once or twice fixes the issue.
For these reasons, I am pretty sure that MY screen flicker is not a firmware/software glitch but is hardware related. Since different adapters perform better or worse, and all are off brand, I suspect that it is poor/weak contacts in the adapter's male usb c plug. It is possible I suppose that there is a hardware problem with the computer, but less likely to me. I have not tried an Apple brand adapter. Regardless, I very strongly suspect that in my case the problem is having a stable, solid connection with sufficient contact for the high amount of data + charge going over it... I also suspect that since rebooting fixes it for some people, we may be talking about the same symptoms but different causes.
