Argh, it was very stable for a couple of days since I posted this. Today, I had to move the monitor and removed and re-inserted the Belkin cable and shoot, the periodic flickering and sleep instability issues are back

I even tried the beta of MacOS 10.12.3 but that doesn't resolve these issues.
I have printed a return label at apple.com and will give it another couple of weeks (return deadline is Jan 16) but if this continues, it is most likely going back. What a bummer, the screen is awesome but I just can't hope for LG to fix these hardware or firmware issues as there has been no acknowledgement from them or Apple and I am left holding a beta lemon product with nobody owning these issues.