Called WD and was told the following.
1. Reformat the WD hard disc.
2. Perform full back up using time machine.
Here is the outcome. I have 830GB on my Mac.
I started the back up at 2:30p.m. It seemed to have stalled at 103 GB and back up slowed to a few MB per minute. However after a few hours, it started up again until it reached 825GB and the dog chasing the tail event happens again. It was 11:00 at night. I decided to leave it there and went to bed
To my great surprise, when I woke up in the morning, the first full back up was successful at 4:00a.m. but used 980GB on my WD. I am not sure where the extra 150GB comes from.
The Time machine has been performing as normal since with back up by the hour automatically. My only obervation is that the time machine icon is no longer turning as in the past during back up. I wonder whether it is OK or not and whether my back up is truly successful? How do I tell.