Galaxy Watch Ultra doesn't detect my sleep

[subseven]

My watch ultra is very inconsistent in detecting my sleep even if I wear it snugly in my wrist and full battery. I woke up in the morning only to find out I have no sleep data. Anyone also experience this? 

[Mogay]

galaxy ring is better for sleep tracking

[Owrayt]

On my watch 7 it has never failed me even on my 1 hour naps it detects it.