After update Apple Watch not charging past 75%

My brand new Apple Watch (one week old with health at 100%) was placed on charger last night and after 50% did the recent update. It reached 100%.

I put it back on, and this afternoon it reached 10% so placed on charger again.

Reached 74% and then after 2 hours managed to fluctuate between 75-76% ON the charger. Yes, lost power on charger.

How can I fix this? Is it an issue with the update?

Do I need to turn it off and on?

Thanks in advance