Tested on iOS.
When launching an experience with the device Portrait Orientation Lock enabled, if the experience has its StarterGui.ScreenOrientation set to ScreenOrientation.LandscapeSensor, the client will incorrectly report the CurrentScreenOrientation as ScreenOrientation.LandscapeLeft despite being in LandscapeRight. This issue persists until the device Portrait Orientation Lock is disabled.
Video of the issue
screenorientation_repro.rbxl (56.5 KB)
Repro file