When One and Seven are on their way to bridge after the Borg Sphere appears they are alone, but as they arrive on the bridge they have acquired a security guard. Surely, if One was considered a security risk (which he didn't seem to be as he was soon given tactical control), he would have had the guard all the time.
When Seven of Nine asks Neelix to bring the first data node to the science lab, he leaves engineering without either data node.
When Seven reveals the fetal drone, Tuvok notices as Seven describes it. How can Tuvok see through that one window on the opposite side of the maturation chamber?