Screen brightness not changing
I recently noticed that the screen brightness on my iMac 27” 2017 model not changing, in precise, from the darkest to 30% brightness bar, it can change, but after that, it just keep the same brightness even though the brightness bar can be increased. When I do reboot, and before screen turns bright, I can see some white spots light up from bottom edge of screen, which looks different from what shows on the top edge. Running Apple self hardware test, it didn’t report any issue. So, what could be wrong, screen backlight, inverter, etc.?
Thanks in advance!