Apple Watch Ultra 2 not recording sleep

Ultra 2 OS26.2 not recording sleep.

After over a year with no issues and no changes to settings my Apple watch has stopped recording sleep data.

I have tried to re-pair with phone, done full watch reset and checked all settings.

I have always used sleep focus on the watch with no issues but since this problem, have tried using a sleep schedule which has not helped.

I have checked the sensors using heart, workout, mindfulness and O2 with all these reading fine. Apple Health reads all info apart from sleep data.

Around 1 week ago the sleep data started recording for 2 nights before giving no data again for the last 3 nights. I have changed no settings, I have tried multiple phone and watch restarts.

Any help appreciated