Laptop display backlight - strange behavior?

Question

Iron

The old laptop began to behave very mysteriously.
Suddenly, the brightness control hotkeys (Fn + F6, Fn + F7) began to work in the opposite direction. Those. The brightness decrease hotkey increases it, and the increase hotkey does the opposite. Moreover, this happens even when no OS is loaded, for example, in SETUP. The F6, F7 buttons work as expected.
The glitch of the hotkeys only puzzled me more, but the real inconvenience is that the screen brightness began to be set only to half the maximum, and then nothing. It's very sad as summer approaches.
If the laptop is turned off and off, then the first 0-2 presses of the hotkeys behave normally, and then they change places. But the brightness at the same time still can not be increased by more than half.
I reset the SETUP settings, flashed the BIOS, I don’t know where to dig further. Very puzzled.
Notebook specifications:
Toshiba M100-221 (M100) model PSAMA0E.
The backlight of the display is fluorescent.
BIOS - Phoenix.
PS The laptop was disassembled for cleaning about six months ago, including the display frame. The glitch appeared recently, but perhaps he simply did not notice before.

Answer 1

To service. I recommend this one (not advertising). In PM, look at what needs to be said so that they also make a discount.

Answer 2

What did the BIOS do wrong to you?! Well, you didn’t have the courage to go and change the RAM or change the battery, well, sorcasm, as a solution, try to change the native drivers to the laptop, I’m talking about the keyboard driver, the one that adjusts the sound, lights, etc. is engaged. In the end, reinstall the OS ...