Trying to Create a custom map for a game but getting weird texture errors. Any thoughts?

Been working on a custom map for a game and have been trying to get my maps to load with their files.
I have been able to load into my own maps by changing the GameDefaultMap in the .ini files but if I use any material
that is not apart of the default engine files I get some very weird texture errors.

If anyone has any ideas into what texture settings this game is using that could be causing this it would be greatly apreciated as im trying to make a map to hopefully apply to them