Definitely a bug. One question on SO was migrated with six close votes. It ended up making two questions on meta after migration.
Is this a race condition with the sixth vote causing the question to be migrated a second time? Could be fixed by either making sure six people can't close a question, or by checking to see if a question was already migrated before migrating it. Assuming that's what the problem is (I've been known to be wrong before).
Both questions on meta link back to the same question on SO, so they were definitely migrated twice from the same source. Additionally, the OP's profile contains only one closed question.
Further evidence: the revision history of the original question is pretty clearly showing that it's been migrated twice because of the sixth close vote:
Post Migrated to meta.stackoverflow.com by Konrad Rudolph, Naveen, Shoban, Daniel Brückner, Yuval F
Post Migrated to meta.stackoverflow.com by Konrad Rudolph, Naveen, Shoban, Daniel Brückner, Yuval F, SilentGhost
Emphasis mine.
Looks like it's not fixed afterall: https://stackoverflow.com/revisions/2030983/list
Was migrated twice due to six close votes. I'm very disappointed in you, Angels.