Apple Watch Ultra not Tracking Sleep Stages

Hi all,

I know this is discussed on here & some users have found solutions, but I still can't seem to get anything to work.

I have an Apple Watch Ultra, running 9.3.1 (at the time of writing). This is paired with an iPhone 13 Pro running 16.3.1.

When I first got the watch, an upgrade from Series 4, the sleep data appeared perfectly, showing stages and tracking correctly. This was working in tandem with Autosleep which I was previously using. No issues for the first couple of months, then suddenly, a few days after an update, the Apple Sleep was just showing the block of time my phone & watch were in 'Sleep' Focus, no information on the stages.

I have tried:

• Verified all tracking metrics are on and allowed under privacy
• Ensured wrist detection is turned on
• Kept watch charged (always 100% at bedtime)
• Made sure Sleep Monitoring is turned on on Apple Watch
• Deleted current sleep schedule, turned phone & watch off and on again, then set up new schedule
• Deleting Autosleep from both phone & watch
• Reset calibration data
• Turned off 'Track time in bed' on iPhone
• Made sure Apple Watch Ultra is first in the 'Data Sources' for sleep
• Reset watch entirely to factory defaults, then set it up again

Sometimes it will randomly track again for a couple of nights & then go back to just the times the focus mode was activated.

This is super frustrating as it links into my fitness apps, which all think I am now not getting enough sleep so adjust metrics accordingly.

Any other solutions people have found other than those already tried above? If not, guess it's maybe a hardware failure.