I have got a TC56 (Android M, BSP21.04.01 LifeGuard Update 09). I followed the tutorial (Set screen timeout interval using StageNow Tool | Zebra ) and created a profile in StageNow to configure screen timout interval in Display Manager.
I scanned the barcode, it works in the first time. When I changed the setting (Settings > Display > Sleep) to another value and scanned again, it failed to change back the setting.
This action works well on TC56 Android M, BSP16.08.01.