That is not a valid configuration, you cannot have multiple buttons monitoring the same device. That won't work.
You should be using some kind of hotdesk, or you can change FOP2 buttons labels "on the fly" by firing a special UserEvent over AMI, but you will have to define how to trigger that event and what name to provide (so actually, you will be using something similar to 'hotdesking').
From the dialplan, something like this:
exten=>s,n,UserEvent(FOP2CHANGEBUTTONLABEL,FOP2Channel: SIP/246,Label: Brandon Roop)
Best regards,
