Before anyone accuses me of heresy, yes, Vaticanus is a good manuscript, and especially in the gospels. But the longer I am working in Paul, the more difficult I find it to treat it with the same respect here as in the gospels. Clearly something has happened in its ancestry, which is, let us say, remarkable.
I don't think the scribe of Vaticanus is responsible for this phenomenon. We have his work elsewhere in the manuscript and I haven't noticed something comparable there. So any tendency only to be found in the Pauline corpus is more likely a remnant of something that happened earlier on. And frankly, I don't think the particular tendency we are talking about is exclusive to Vaticanus, it may share this tendency with a number of other manuscripts, in particular the Greek - Latin bilinguals. But it is at times quite pronounced in Vaticanus, more so than in the others.
So what is the vice we are talking about? Hold your chair. It is that of reversing the order of the name-title 'Jesus Christ'. And Vaticanus will almost always be at the side of the order 'Christ Jesus'. In Romans, for example, it is the singular reading of Vaticanus in 5:17, 5:21, and 16:27. And elsewhere it has 'Christ Jesus' often with only minimal support from others (regardless of whether it is deemed to be the original text or not), such as the Latin bilinguals, or minuscules 33 and 81, or Sinaiticus (and it may be that each of these three combination agreements have a different meaning).
I said that very often Vaticanus will be on the side of the 'Christ Jesus' reading, but not always. In Gal 2:16 we find the collocation Jesus and Christ twice, in either order —and twice Vaticanus gets it wrong (I agree here with NA27). Anyway, all this is leading me to a rethink of quite a number of variants, because it seems to me that, strong though Vaticanus might be, we have hit a particular weakness here.