This is my sleep from Oct 30 to Oct 31. Where I live (Switzerland) at 3:00 AM the clocks are set back to 2:00 AM because of daylight savings time. That means that I had one hour more sleep. You can also see that the REM phase in the middle is very long. I think there was a light sleep phase there but it wasn't recorded or overridden.
I have a Garmin Instinct Solar Tactical with firmware v16.0 and a Samsung Galaxy S10+ with Garmin Connect v4.48
I think this post about the Fenix 6 is related: https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/fenix-6-series/274561/daylight-saving-bug-with-sleep-and-body-battery-19-20