Exporting a sphere to a custom model loses nodes. On a 72 node sphere across 8 strings, 8 nodes are dropped.
Steps to recreate:
1) Create a sphere. In my case, 8 strings of 9 nodes. The issue was found on 2019.68 and also recreated on 2020.3
2) Export sphere as custom model. Inspect the export file and node numbers will be missing.
3) Alternatively import the model into a layout. There are missing numbers across the 17 layers the sphere is laid out against.