Reproduction steps:
1. Open the attached project "ReproProj"
2. Open the “/Assets/Main Scene.unity” Scene
3. Enter the Play Mode
4. Observe the Console

Expected result: No Errors exist and the Cube moves up and down
Actual result: Error "Internal_SetPosition can only be called from the main thread." is present

Reproducible with: 6000.3.0f1, 6000.4.0a5, 6000.5.0a2
Could not test with: 6000.0.63f1, 6000.2.14f1 (Assets\UserAssembly\SampleComponent.cs(24,12): error CS0246: The type or namespace name 'TransformHandle' could not be found)

Reproducible on:
Play Mode

Not reproducible on:
Windows Standalone Player

Testing environment: Windows 10 Enterprise 21H2
Not reproducible on: No other environment tested