Weird line spliitng in when using Nvidia Index

Hi all. I am using Nvidia Index to do some volume rendering work. There is something weird in my figure which shown in the attached figure. For your information, I will need to extract the section to use Nvidia Index because my graphic card does not has enough memory to rendering everything. I have try to apply tetrahedralize filter to the extracted section but it does not work. When I change to Volume, the splitting line does not show up.

Thank you for your concern.