ZDoom

But it's truly peculiar how these bugs seem to be a one-time only kind of a deal. I have no idea how they get triggered and I can't reproduce them outside of mark's save files at all either.

That's some real nonsense for sure.

I can outright tell you that I won't be able to do much here unless I have a working level viewer that works on Windows and lets me analyze the setup of the level itself.
It's already bad for Duke - Mapster and I are not compatible - but with Blood it's even worse, because there's only DOS tools.

Blacked out torches. Again shows up when doing a normal playthrough, always looks normal when I try to reproduce. :bang:
[imgur]https://imgur.com/TflA08J[/imgur]
Save file: https://www.dropbox.com/transfer/AAAAALe_7T_uzfoDb_LD42VYUoF8r3ofki5aN_ZoCXi27tMX2xyu27c
(Is it a coincidence that it happens in the later episodes?)

Maybe I encountered a variant of this bug. Notice the veritcal streaks. Unable to reproduce. However, my original run that triggered it involved a lot of quick saves, just like OP.
[imgur]https://imgur.com/TydDax1[/imgur]
Save file: https://www.dropbox.com/transfer/AAAAAEo3SQCEobrmDwuvQKZEOBigdXbkhaCSp1GS3zY-qP6lnLz4U8c

Tried taking this route myself multiple times to see if it changes anything but no luck, in both NBlood and Raze.

I noticed that the room with the Tesla is also abnormally dark, so it's not just the outside area, but the whole map. My suspicion is that the light values didn't get set properly that time, and they got preserved in the save file. That should be good for troubleshooting.

I progressed through the two skull doors in order and eye door before steeping outside. I noticed the skybox is darkened too, I don't see it looking like that normally.

Hm, that's odd. I can definitely reproduce it consistently when loading your save file, but it returns to normal after simply restarting E4 again.

Could it be something in the map that failed to trigger or something? How did you progress? I noticed that the green window upstairs where the secret armor and a key was isn't broken.

The outside area in this map is darker than in NBlood and DOS.

[imgur]https://imgur.com/gw5a01K[/imgur][imgur]https://imgur.com/Mv4jZes[/imgur]

EDIT:It's inconsistent, I tried to re-create it but this time it looked normal. So I can't confirm it's limited to Raze. Never the less it's documented in my save file: https://www.dropbox.com/transfer/AAAAAFJS_BUiP7NDxAV5v9VPbc1cO-YQfZakkabdo41z4OUfC-vXlpk