Steps to reproduce:

• Create new host, add some items to it( lets call the host hostA)
• Clone the host, save it: all good (lets call the host hostB)
• Now create a graph that references item from hostA and item from hostB → that just works
• Clone hostA (or B, doesnt matter) and try to save it. You will get an error message 'Graph "testgraph" already exists on the host "hostA"'