It seems like the issue may be some broken logic with regard to the main brightness slider and maybe adaptive brightness.
I am able to get it to break in reverse too. Enabling the status LED slider and putting that all the way to the right, but dimming the screen with the LCD slider all the way to the left will brighten the LEDs, then upon disarming they dim to match the screen level.
I hope it will be fixed soon. As you recall, this was a new feature awhile back, but broke with the next update. I would think that they could easily fix a problem that they caused themselves.