ZDoom

1. Windows 7
2. GeForce GTX 1060 3GB
3. It only started happening part way through Sunder map18 and from the beginning of map19
I was able to reproduce it by running GZDoom 4.10.0 with Sunder 2407.wad warping to map19, and clearing the first arena and saving.
4. I was on Vulkan.
OpenGL ES and OpenGL both save display normally when saving, I tried loading a corrupt save and saving it and it displayed properly.

The savegame won't really help. This looks like the framebuffer readback from the GPU does not work, so the most important things here are:

1. What operating system?
2. What GPU?
3. Is this specific to these maps? If yes, only specific to certain places in the map?
4. What render backend? Does changing this make the problem go away?

Probably also upload the save games in question.

You should know the drill:

What's your hardware config and which render backend did you use? I've never seen anything like that on any map I played.

The image accompanying saved games on Sunder map 18 and 19 buggy.