Texture format... I think?

I made a mod, for which I changed a texture,  and saved it under a new name. If I run it as a local mod, everything's fine, but when I upload the mod to mod.io and then subscribe to it, the game gives me the following error messeage, about one of the two texture files I made:

d3d11_file_texture::create_device_resources failed. path=[C:\Users\Public\mod.io\5762\mods\4271160\textures\PsiMediumlLaserBeam_Core_clr.dds] error=Ende der Datei (EOF) erreicht.

 error_code=0x80070026

I used GIMP with a dds plugin to make the file in question.

Does anyone know the exact dds file format, Sins 2 uses, or how I can read the specific format out of the game files? Maybe specifying that format, rather than saving as "default" will fix the error.

....but why does it work as a local mod, but not a subscribed mod? oO

I also just found out, that there are some dds files in Sins2 GIMP can open, while others are in an "unsupported DXGI format (98)"