Your image is not exactly "seamless" - I took it, applied it to ground plane, repeat 2 x 2, seamless ON. Looks like there's discontinuity 1 pixel wide?.
Set mine to bump and turn the model around . Three of the four quadrants seam up together just fine. One does not.
If the one pixel discontinuity is a problem, it would be a problem at every join, not just for one.