Apple Watch 8 stopped measuring the wrist temperature

Hello, I have noticed that my Apple Watch 8 has stopped measuring the wrist temperature around 3 months ago, simply from one day to another. I have no measurements since August 2024, which by then were regular. What can be the reason for it?

The watch didn't have an accident, didn't get flooded etc. I haven't changed the size of wristband, it sits quite tight as usual, for one night I have checked even a tighter fit, but it didn't result in starting the measurements again.

In the Watch App the toggle "Wrist temperature" is "on", I have an active sleep schedule, don't know what other settings I should check.

Simple restart of the watch didn't help with the missing temperature measurements either.

The Watch has watchOS9, cannot be updated, because it's paired with Iphone 8 that doesn't get updates above iOS v. 16.

I am out of ideas for now. Many thanks in advance for your hints!