No one else has this problem? It's starting to become a deal-breaker because I have to constantly change the panel brightness back to high (high doesn't seem to affect gamma/saturation with content: graphics like it does with content: off, so I use high).
edit: Here's the sequence of events if anyone else wants to try it out (confirming that others see it would be a big help)
1. Using any HDMI content type in custom mode
2. I go into Pro settings and change the panel brightness to high. The image is bright, color-accurate, and colors pop.
3. I watch TV normally for about 5-10 minutes, and then I notice that the screen has become dim.
4a. I pause the TV and go into pro-settings and change the panel brightness from high to mid. The screen actually brightens when I do this, instead of dimming like you think it would. When I change it back to high, the image brightens further. This means it actually reverted to low in step 3, even though it says it remained on high.
4b. Instead of changing it from high to mid, I change it from high to low. The screen flickers briefly but panel brightness remains exactly the same.
5. Steps 3-4 repeat indefinitely while the TV is on. If it's in between steps 3 and 4 and I restart the TV, it will brighten again and be after step 2.