1) I tested first your texture on GTR Evo Offline :
file in GTR Evo\GameData\Team\LENS_FALRE_SUN.dds
track : anderstorp because there is a big sun;
now the game crash at the end of track loading (initialization) !!???!! ;
2) then I tested your texture on GTR Steam;
here no crash, I can drive on anderstorp; but now the sun disappeared,
3) Then I tested on offline and steam with the sun mod : it's the same,
4) Finally, I put back original sun texture in GTR offline , then KO !!!!! (same as first test)
5) Finally, I deleted sun texture in GTR steam ==> idem second test !!
It's looks like as if the problem is now stored in the game
Why It is impossible to open original sun file texture with DDS converter 2 or paint.net ??