I created the description.lua file in ModelViewer and also got the texture files from C:\Program Files\Eagle Dynamics\DCS World\ Mods\aircraft\F-16C\Cockpit\Textures\F-16C-CPT-TEXTURES.zip. Even though I didn't make any changes to any of the files, I encountered this issue. In other words, I encountered this issue even though I didn't change any of the files provided by the game. Therefore, this is probably a problem with the game.