Watch series 3 locks while wearing - only since WatchOS 6

if I set wrist detection off then the watch does not lock except when I put it on the charger, and I am running the same apps (Weather, Now Playing, Activity Monitor, Calendar).

Ah, good clarification. It's clear an interaction between the wrist detection setting and something going on with the apps.

I initially thought the problem was the wrist detection setting in general, so I tried tightening and loosening the strap, jumping up and down, etc. I could never get it to do anything.

Then I started launching apps, and I could get it to repeatedly crash in an app and immediately dump to the lock screen.

If you google the issue of "apple watch keeps locking" it's clear that in the past there have been problems with the sensors themselves. It seems to me that is NOT the problem here, but some sort of interaction between the wrist lock setting and something running on WatchOS 6.0.1.

Does your wife's watch have the wrist lock set to ON or OFF?

I guess this gives me the option of continuing to run 5.3, or upgrade to 6.0.1 and turn off wrist detection. I've owned an Apple Watch since the Series 0 and have always used wrist detection.

Like many others, with the update to WatchOS 6 on my series 3 Watch, the hardware sensor on the device is no longer “correctly” determining that the watch is still on my wrist .... this is (in my opinion) a software “bug” that has been introduced with the latest WatchOS 6 version. Something has changed, which is causing the sensors to incorrectly believe the device has left the users wrist (be it greater sensitivity, reduced latency in determining lost contact, etc). It is extremely annoying, and this flaw is reducing my security, because I must disable the wrist detection option so I’m not constantly being request to unlock my watch ...

https://www.reddit.com/r/AppleWatch/comments/daucld/anyone_elses_watch_keep_locking_after_update/

https://discussions.apple.com/thread/250689941

https://forums.macrumors.com/threads/apple-3-locks-throughout-the-day-randomly.2201726/#post-27804947

See https://discussions.apple.com/thread/250684967

I have an issue that might be similar, not sure. In my case the 'Unlock with iPhone' option is not available and the entire Passcode menu is loading indefinitely. As a result I need to enter my passcode every time the Watch gets locked. I used a S3 Watch for 2 two years without any issues.

Is this somehow maybe related to your problem?

Hello and welcome to Apple Support Communities, PhantomFrank.

If I understand your post correctly, your Apple Watch is locking while your are wearing it. I’d like to help.

This guide will show you how to control locking on your Apple Watch:

Unlock Apple Watch

This guide will show you how to keep your Apple Watch on:

Turn on and wake Apple Watch

Let us know if that resolves this issue for you. 

Thanks for using the Apple Support Communities. Take care.

I have the same problem.

But as I posted in another thread, I don't think it has anything to do with the watch sensor and wrist detection. The problem is that the watchOS itself is unstable, an app is crashing, and the crashed app locks the watch.

On mine I could reproduce the problem by launching various apps on the watch. Eventually one of those apps would hard crash, and the crash would result in Watch being locked. Often the weather app would crash in this way, and every time it would lock. The now playing app would function similarly.

apple support. Obviously you have not read the original issue. Maybe before you throw out one of your standard answers lease read the issue then provide adequate responses.