Sleep Tracking not accurate

I recently have a newborn. And as you all know... sleep is hard to come by when a baby is keeping us up throughout the night.

There are several times throughout the night where I get up and go to the nursery and it takes at least an hour for me to get back to sleep when I go back to bed, and yet my Garmin Forerunner 245 logs some sections of the night as “light sleep”, and even on some nights as REM sleep... even though I am moving around and definitely not asleep.

Pretty disappointed as it has the Pulse OX tracker, respiration, movement and heart rate to try an accurately record my sleep. I feel horrible in the mornings after clearly only sleeping 4 hours, and the app logs 9 hours sleep!? 

Anybody else who is experiencing something similar?