maybe the rms error is above the 0.05 threshold?
Does it look like that? And also I have calculated it already. It is not more than that.
RMSE looks fine. 0.05 limit is quite loose. I think it would be more linearity check that cuts it off. In X0 you have quite a variation of line slopes.
But more importantly - very nice coverage! I would be supper happy if my models were returning something like that.