I think that the 10th data point in your model is an outlier. Could you test it again 1) by adding 11th data point, 2) without 10th data point, 3) with 10th d

I think that the 10th data point in your model is an outlier. Could you test it again 1) by adding 11th data point, 2) without 10th data point, 3) with 10th data point corrected?