Large area of map displayed with 100% brightness

Two years have passed, and it still happens, even in DLС.

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The biome background colours appear correct though. The borders of the background areas correctly match the abyssalite zones.

Some further information:

• This appears to happen in other seeds as well, in fact every game i've started recently.
• In my slightly older game started sometime around update 456940 behaviour seems relatively normal. At least no different from the base game. It still does the wonky max brightness thing but only a little above the magma, not several biomes up.
• When i load an older game the display is unchanged from how it was, the bright area is still only at the bottom of the map, so it seems to be baked in at map generation.
• From what i remember this is happening since about update 459378 which added the Classic starts, and perhaps relevantly, raised the map ceiling on Spaced Out starts.