I'm having the same problem went to tge shop today ask them why they asked me I'd I've had an update recently told them yes had one yesterday the said that the reason and I need to reset my watch to factory settings and set it up again told them it's been happening before the update they had no answer then
Many have come across battery issues...and are not recommending for S Wearables...better buy a cheaper ones MI or Huawei they have all the features of S and 5 day battery life.