I was wondering what causes custom textures in my map to either be missing or become very pixelated/glitchy at random times. Is it an issue with my memory, am I compiling the images wrong, or something else?

It always happens from time to time. There's no stopping it.

If you want you can send me the brushes or patches in a .map with any lights nearby and the gdt entry for the custom textures.
You can copy entire gdt entry to the clipboard from asset manager by clicking the copy button with the texture selected.
I dont need the actual dds tga or iwi textures.