Facies computations

[Saman-M-B]

Hi,
Using Archpy, I'm encountering an error while computing the facies realizations. I suspected that the covariance model I defined for Unit B is somehow not a good fit resulting in this issue because Unit C works just fine. I'm following the examples of ArchPy so I thought at the beginning let's take a simple approach to just see if the model works with my borehole dataset and then optimize the methods and covariance models. Any idea what might be the root causes?