A visual interface bug that prevents you from exiting the brightness tab without a brightness bar and only the Creepers appear.
GUI interface graphical bug Screen dimensions issue in the brightness sub-tab in the Vibrant Visuals graphic section. The brightness slider buttons are not available on some Android devices... By the way, a bug in the buttons that prevents an optimal and inconvenient experience for the player is the only error I found while using the settings for the new vibrant visuals. The bug occurs when pressing the brightness button on some Android devices, for example a ZTE Axon series which is a mid-range device, the shaders can be in a decent way around 30 to 60 fps.
This issue is being tracked at MCPE-208098.