According to Ubisoft's support document, I can replay memories. However, I screwed up in Sequence 1 Memory 3 (A Journal of some kind) but it seems I cannot repeat it, the option is simply missing (this is true for all of the memories in sequence 1 so far; haven't completed the sequence yet so I don't know whether this issue is with later memories as well).
So are there memories that you are not supposed to repeat? Do I have to complete the sequence first? Or is it a bug?