Thanks for the files, pinareris, even this is the third pair of shoes, not the one with the problem. But I see a pattern here. Thanks for naming the target app.
However, here are some tips:
Don’t put your textures into the Environment channel. This is for equirectangular images (360º*180º panoramas)
Do not set the texture to offset 100%, 0% is just fine here.
Check that your UV data is inside the 0,0 to 1,1 UV area, just in case. (Offset puts it out. Not all apps can handle that.)
There are polygons where I have no idea why they are in the file and why they need an Alpha map to be hidden. I would delete them (Sole to heel triangle.) If possible, avoid alpha channels. Your models have the option to precisely polygon select areas, use a material that allows for an alpha just for that area if there is no way around them.
If you encounter problems, convert the PNG to a JPG just to see if the problem persists. I find 8bit/channel images should have no place inside a production pipeline for many reasons anyway.
Avoid transparencies in PNG, which is the official information of ClO3D.
After you created an FBX, use a fresh new C4D scene and merge the FBX into it. Just for the peace of mind. Consistently deliver the fbm folder with the FBX.
Enjoy your creation; I hope the tech will not be in the way of your design anymore.