What should I check if HDR brightness upscaling flickers while scrolling?
Compare the display with variable refresh rate disabled. Some monitor configurations flicker during HDR brightness upscaling while adaptive refresh or a linked gaming mode is active. Testing a fixed refresh rate helps distinguish that interaction from the brightness adjustment itself.
Keep the other settings unchanged and select a supported fixed rate. Check the monitor's own menu as well: its Game Mode may enable or govern variable refresh. If turning that mode off stops the flicker, you can keep the fixed-rate configuration or leave brightness upscaling off when using the gaming mode.
This comparison does not establish a universal fault or fix for all HDR displays. If flicker continues, compare upscaling on and off and record the monitor, connection, active adjustment method and refresh mode. See Refresh Rate and Image Adjustments for those settings.