Apple Watch Series 6 battery drain

Since about 2 months (I guess around watchOS 9.4), my Apple Watch’s battery is suddenly draining very fast. In late afternoon it’s empty while usually I still have about 20 to 30% before I go to bed. It's a huge difference and not due to battery age or health. I always charge it at night. When in the morning my Apple Watch is still a bit warm, I know it’s going to drain very fast: 10% after about an hour. Before the draining problem, it was completely cool and I can see it was already charged to 100% for a few hours before I picked it up.

What I’ve tried: rebooting Watch and iPhone, unpairing and restoring, deleting all 3rd party apps and using it for 2 days, deleting all watch faces and using it for 2 days.

Some things I observed:

• Updating to iOS 16.5 and watchOS 9.5: the problem went away for about 1 or 2 days but came back
• Disabling Bluetooth and connecting directly to wifi solves the problem (although this should give you less battery life)
• For each day I’ve got a few JetsamEvent log files where the largestProcess is always “ClockFace” (that’s why I deleted all my watch faces but that didn’t work)

Apple Watch Series 6 and iPhone 13 Pro, latest software versions of everything.

Anything else I can try?