This is peculiar, because I didn’t actually have this problem with my project until recently. Somewhere along my blueprint chain, I have a simple “Set Material” hooked up to a static mesh component of an object in the level, changing the material of element 1 from plain black to a 2D render. The only problem is whenever this event executes, it sets the material to the default-ish light gray/dark gray grid checker pattern. I even hooked up a print string after the “Set Material” action, which prints out the name of the material that’s currently on the same element - and it says that the one I want is applied. I don’t know what’s wrong, because I had this hooked up before, and it worked then.
Picture for reference: