Aspose.PowerPoint is not working correctly with nested groupshapes, please test it (((GroupShape)shape).Shapes doesn’t contain all shapes).
Well, I tested it:
1. Created new presentation.
2. Added 2 shapes and grouped it.
3. Added 2 new shapes and grouped it with the first group.
4. In debugger I see 1 GroupShape. It contains nested GroupShape and 2 other shapes. Nested GroupShape contains 2 shapes too.
I have sent a problem ppt file to you.