The result of the k calculation using OpenMOC diverged

Hello everyone, since I can’t access the OpenMOC forum, I have to seek help here. When I use OpenMOC to verify the cross sections generated from OpenMC, I replaced rod elements with plate elements, and I noticed that the k calculation keeps diverging. However, if I set the energy groups to a very small number like casmo-70, k converges. Is this due to the specific nature of plate elements? Can anyone help me with this?Here is my input,Thank you!
mgxs-part-ii.ipynb (285.6 KB)