Garmin fenix 6x sapphire not detecting REM sleep

Hello i have a strange situation with my 1 weak old fanix 6x sapphire, from beginning 5 day is ok sleep detecting deep, light, rem and awake but from 2 day only deep, light and awake but the deep is 2 time more long from before, like deep and rem sleep is united together

SV:4.30 GPS:2.60 WI-FI:2.60 CIQ:3.1.4 BMX:0.5.1 WHR:20.04.40 ANT/BLE/BT:4.30 Sensor Hub:2.60