Thanks for the suggestions. I used a high speed HMDI cable. It worked flawlessly the first week. Then after that, the CEC power doesnt seem to sync well; then the TV audio doesnt get to the AVR via eARC; then the eARC doesnt seem to shift the audio when I change media source.
By the way my set 5.1 is: marantz AVR (thats eARC ready) with a separate AMP for the front speakers. I have an NVIDIA shied as a connected media source.
As a temporary solution, I turned off eARC. I then connected my TV output to the AVR via an Optical Cable.
If I want to watch using NVIDIA shield, I manually chose the designated HDMI port. And, If I want to watch via the LG CX Apps, I chose the TV Audio Port in the AVR.
Alls fine, except that ang dami lang pinipindut na remote (TV, NVIDIA, AVR and the Power Amp for the fronts. hahah), not to mention the manual switch for the Rel sub.
Until I fix this software cable, am thinking of using a Harmony Remote/Hub that I bought 2 years ago but havent unboxed.
Except for the above kink, the OLED experience, with the 5.1 sound is just a major upgrade in viewing experience. No regrets.