Power manager dims screen when laptop is plugged in, even when told not to
On the display tab of the settings dialog, I set the "plugged in" brightness reduction to "reduce to 100%", and "reduce after: never":
With those settings, I expect that the screen brightness will stay the same, regardless of how long I leave the controls alone. However it still dims the screen after a short while.
I guess it's because it incorrectly thinks the battery is discharging? The laptop is plugged in, and the indicator light next to the power cord is lit: