[winkydink]

So last night I attempted to do some other tests with the TV.

A thought occurred to me, that it might be the "converter box" that converts the HDTV signal into NTSC. So I eliminated this from the input signal chain.

I instead had the following setup.

Roku device (HDMI output) => HDMI to RCA (Composite) converter => Component to Coax converter
==> Coax to Twin Lead converter => TV

When I ran the TV this way and played a show from Amazon Prime [Fraiser - it had 4:3 aspect ratio], my set DID NOT experience any flashing or losing vertical synch between different scenes. I played this for the entire show with out any problems.

I did notice that when the signal turned from 4:3 aspect ratio to 16:9 (for a commercial), I did get a flash and temporary loss of vertical synch.

I guess bottom line is that my HDTV to NTSC converter is low quality.