Watch losing time and step count at night?

So what's actually happening? Between 10 PM and 11 PM what actually gets displayed on the screen?

As far as I can tell, at some point between 10 and 11 pm, the time gets set to some random value in the past and step count drops to zero. This incorrect info gets displayed on the clock, as if that was the current time. Or, if I have some other app open, the clock widget (widclk) displays the incorrect time. Also, since my own stopwatch app works by storing the start time and displaying time since start, it displays a very large negative time.

And does pressing the button once to enter the launcher and again to exit it fix the issue?

No. Doing that, or just generally switching apps, does not fix it. I've been disconnecting and reconnecting my phone to force a time sync to get the time back.

I guess as a starting point, it'd be good to make a note of the actual time when it happens and to make a screenshot (you can do that from the app loader now).

I don't catch it at the exact moment it happens. I only notice it some amount of time later when I look at my watch to check the time and notice it's displaying 2 AM or something. But I guess I can make a note of when I noticed it. And nothing weird shows on the screen, but I can definitely still take a screenshot

If you can be connected with the Web IDE when it happens, you might find there's an error message displayed which really helps to track it down.

Good idea. I'll try to have my watch connected to the web IDE at 9 PM and look for any error messages.

Also, very importantly, what clock face is it?

My own clock face, infoclk. Maybe I'll try another one if it keeps happening.

It could well be there's some bug in the clock face - I guess maybe if some code fails, it could not update the time/step count variables correctly and then they end up displaying the wrong info.

I thought the clock face only displayed info, and wasn't responsible for actually setting it?

Also, it did not happen last night. But I will try to be prepared tonight.