Cutting into belt

What could have happened that the roller in the right-back of my V-Core-3 is cutting in the belt?? It seems to be too high on the roller, but only on this one, the rest have no issues. It seems to be going on for a while, judging on the amount of rubber-dust, but I just noticed it. Nothing has been dis- or re-assembled since the initial assemble more than 3 years ago. Never had any issues, besides the regular ones 😉 See attached pictures and shot video for details.