Ensure that the input .vmdk file is the .vmdk file that the .vmx file points to. The .vmx file points to a .vmdk file that ...

Ensure that the input .vmdk file is the .vmdk file that the .vmx file points to. 

The .vmx file points to a .vmdk file that contains metadata. That .vmdk file in turn points to a binary .vmdk file. With the Copy-VMDK cmdlet, use the .vmdk file that contains the metadata. 

Additionally make sure that both .vmdk files are not corrupted, and then try the operation again. If the problem persists, contact Microsoft Help and Support at http://go.microsoft.com/fwlink/?LinkId=45276.