Hi John,
UPDATE:
Please omit first two paragraphs, I think I've solve it. Going to do another cal ride early in the morning later.
I've remove and made new pairing on my garmin watch. Also did cal ride, seems the cadence sensor not being pick up by the pod. I've also replace new battery to the cadence sensor before i did as per your recommendation. Any other remedy for this?
Earlier days setup, I'm using both Garmin watch and Bryton 310 to record my ride and pedal stroke was fine. Which till today I still use both device to record my ride. Only thing not sure what went wrong this time around...
As per descending, I was in tuck-in position...aero all the way..

, oddly pod assume im crunching out 200w

but I do occasionally spin very lightly
Many thanks again tending my problem...
Cheers,
Norman