Synchronous copy of group with MPP results in flattened MPP?

I have a strange problem when I copy a mpp within a group. After the copy I end up with the original MPP but also a flattened version with only the subparts.

I perform following steps:

1. Create 2 new mpp and group them together.
2. Make a synchronous copy of this group.
3. Result:
   1. The original MPPs
   2. A flattened version of each MPP, without the main path (subparts only).

This is specially a problem if you want to use synchronous copy. The copied group is not the same as the original and is removed from the clone family.

Selecting 2 MPPs and make a synchronous copy directly has the correct result. However, copying one of the resulting clone family members has the same problem as described above.

The CDS version I use is IC6.1.7-64b.500.4