Combined brightness control issue on Mac Pro (2010)

[Fred-IV]

I cannot tell you when this started, only that is used to work, and failed recently over the last few versions.
I wish I could be more exact.

When I shut off my monitor for the night, I turn down the brightness on my monitor using the keyboard, and reduce it maybe 80% less, so it's very dim.
I do this to lower power to my video card, and save the screen, if I leave it on, but this particular bug is after being powered off for hours.
I leave the computer on 24/7, so this is my way of leaving it. I do not sleep it either.

Now, recently, again, within the last few versions, when I power the monitor back on, and use the keyboard to brighten the display, it is dim, and will not turn all the way back up. Maybe only 80% of full power, and the display HUD popup is maxed at 100%.
If I keep pressing it anyway, and it cannot go any brighter, and the Mac thinks it's at 100%.

I've been trying for a while to fix it, trying settings, resetting them all, everything I can, and only one thing fixes it. I have to kill BetterDisplay, and re-launch it.

killall -9 BetterDisplay && sleep 5 && open /Applications/BetterDisplay.app

Then, I can turn it up and down as normal, until the next night, and I power the monitor down for the night again.

BetterDisplay Version 3.3.0 Build 36506

Viewsonic XG2705

Mac Pro
Mid 2010
Processor 2 x 3.46 GHz 6-Core Intel Xeon
Graphics AMD Radeon RX 580 8 GB
Memory 128 GB 1333 MHz DDR3
Startup disk CMP WS 2010
Serial number
macOS 15.2 (24C101)

[waydabber]

Technically this Mac model might not be properly supported by the app as it cannot run any supported macOS version without OCLP and various hacks, and some of these might interfere with how the app works. In order for the app to support proper color table dimming it needs to establish a baseline (based on the current color profile) during detection time and this is where things might be messed up. Alternatively some other apps might interfere (f.lux or any other app that also adjust the colortable). The issue will probably be fixed if you disable color table adjustments in the app (in this case the app should use DDC + overlay dimming for combined brightness control).

If you downgrade the app to some older versions, do you get similar results?

[Fred-IV]

The issue will probably be fixed if you disable color table adjustments

ok, disabled. Will try it for a while and report back if it fails again.