I've moved your1.com to your2.com
I want to move your2.com to your3.com but I'm not allowed - see this image:
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While I can't find documentation to verify this claim but I have always believed that Google has a cap on how many times you can do this within a set time period. This is to prevent people abusing the system.
Quote from Google
To prevent confusion, it's best to retain control of your old site domain for at least 180 days.
While this isn't direct proof I would consider that maybe there is a limit for 180 days, or until the old site is completely transferred over, have you checked to ensure that all pages are cached, indexed and the old site is de-ranked completely? You should also not see the MOVING of the old site in the control panel, unless you are sure 100% has been done the remove it.
Additionally I'd like to add you need to be extremely careful with these moves, you always lose some juice with any 301 redirects and moving of sites otherwise people would just move there sites all the time to get out of Penguin. It's also worth noting that if your doing this because of Penguin and not re-branding your be annoyed to hear moving site passes penguin slap across. Only way is not to move it and set it up on a new domain with no 301 redirecting.