Hi,
I'm having the exact same problem, did you ever get any solution to this problem ?
I can successfully add four vCenter but when I add vCenter server #5 it replaces vCenter server #4, if I add vCenter #4 again,it will replace
vCenter server #5....
The two vCenter Servers that I fail to have added both at the same time are both very similar but they are located at two different sites.