Since upgrading to OS 9.6.1 my Apple Watch 6 has been overheating and shutting down regularly. Unusable to track Exercise and Health. Any ideas, please?

• Apple Watch 6 (from May 2021)
• Upgraded to OS 9.6.1 in August
• Overheating symbol and shuts down regularly even when in air-conditioned building and normal temperatures and NOT charging
• Battery use and charge hold worse after upgrade, battery life/max. capacity is at 80%
• Watch does not feel hot when overheat symbol comes on
• Not running many apps (and shutting them down) and not storing much.
• It 'overheats' and shuts down when running just an Exercise tracking like Walking, no other apps
• Only 6.4 Gb of 32 Gb used, so 20 Gb free
• GPS only NOT cellular
• I have tried the unpair and re-pair with my iPhone 13 Pro and tried the full erase on the Watch. Did not solve issues.
• Prior to upgrade this watch worked perfectly and with satisfactory battery life.
• Very frustrating that a so-called upgrade needed to cover security issues (plus other stuff I do not need) has effectively ruined a $400 watch that is just over 2 years old.
• That cannot be acceptable obsolescence.

Any thoughts appreciated? Discussions seem to suggest others with issues with OS 9.6.1. Thanks.