Not that I know of. You can add many WAD files to a map that are then combined to the $$W. Maybe one of the textures is damaged or has an unsupported format, invalid characters in the name or something like that?
the point is that I can add either one of the wads and it works fine. However, when I try to add both wads on the same level the error appears.
3D Gamestudio A8 Pro AMD FX 8350 4.00 Ghz 16GB RAM Gigabyte GeForce GTX 960 4GB