I had a small revelation(!) However, this may be a 2D only thing and I'm probably using the wrong technical terms:
It seems to me as if the repeat function only works properly if applied to a 4x4, 8x8, 16x16 and so on -pixel sprite. Other, "uneven" formats will result in smeared edges or simply nothing at all. In this image, sprite 1,2 & 3 were uneven (9x8 & 66x32 pixels) and the bottom sprite was a 16x16 sprite.