Sloped 3D Floors not displaying correctly about gzdoom HOT 5 CLOSED

Please provide a runnable WAD file.

As a general rule of thumb, images are next to useless for debugging purposes in (G)ZDoom.

If you don't want to share the map publically, you can PM Graf Zahl on the forum for the map. Don't forget to reference this issue in your PM.

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The screenshot doesn't tell me what this map is doing that is wrong. Be aware that this isn't a general problem, I have played countless maps recently which looked fine.

So yes, I absolutely need the map to see what is wrong here.

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Also important: What is your graphics card? There are two processing paths for sloped walls, depending on hardware features.

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K, here is my map WAD, and it is MAP02.
https://www.dropbox.com/s/2qdas50pyj6dzj9/map02issuewithsloped3dfloors.wad?dl=0

I've moved the PlayerStart to right under the bridge for convenience.
I didn't batch in my resource file/decorates, so the monsters are conveniently absent. You'll see some carefully placed <!> sprites in the area. If this pose any issue I can then zip it up with my resources and send privately to Graf.
I run this over Freedoom 2 and FreeDM, but I checked it in Doom2 as well, to make sure it looks about the same.
I'm not sure what I could be doing wrong that would still let it work in an older version, other than possibly some random default display setting I need to change?
I have an EVGA geForce GTX 960 SSC.

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Why does this sector have a type of 90? 90 is for marking special skybox sectors and interferes with other operations. This type was added after 2.1.1 so it just went by unnoticed in older versions.

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