Sorry, it seems that I have an error in the PR4100 observation.
Today, this LCD can not be turned off and repeated tests, put the computer next to the pr4100, including upgrading the firmware again (2.30.193), only the system is restored to the default settings, the LCD is turned on or off, and the screen backlight remains the same brightness without change.
When I reverted to the firmware version 2.30.165, the LCD was turned on or off, and the backlight of the screen remained the same brightness without change. However, in the previous firmware version of this PR4100, the LCD backlight will be turned off, and the backlight brightness of the LCD will be lowered. When the upper or lower button on the right side of the LCD is operated, the backlight brightness will increase and will decrease after a few seconds.
It seems that this error belongs to the 2.30.193 version of the bug. Even if you restore this firmware to a previous version, you will not be able to restore this feature.