@vanex 

Is there any abnormality in the color of the light strip when it is set to a solid color, such as red, blue, or green? (Can be switched through my presets) Does this issue occur when using the app or when using the controller button to turn off?

Do you have any extra controllers, or another working L900? You can try switching controllers to see if there is any change.

Can you also share some pictures about this issue here?  And also some picture when it's set to a solid color, just for comparison.