Hey! This seems to be due to anti-aliasing trying to blend between two UV values that are at extremes. For example. One pixel with a UV coordinate at 1.0 might be next to another with a coordinate at 0.0. A naïve anti-aliasing filter will try to blend between these two pixels and create a value like 0.5. This causes the strange artifact at the seams that you see here. You will want to ensure that the UV pass you export does not have any additional filtering or anti-aliasing so that it does not introduces these intermediate values. I believe in C4D's render-settings you can set Anti-Aliasing to "None" and it should remove these seems.