The problem with the three scenes left in the novel is that in order to make one of them work, I’m going have to go back and tweak about four or five other scenes, because in order for the character in question to do the thing he’s about to do, it turns out that he needs to know something that he currently doesn’t. I could just tell myself, “Assume the knowledge and fix it in the revisions”, but my mind doesn’t work that way. If I don’t go back and fix those bits, the scene will stubbornly refuse to gel.
At this final stage of the game, my distractability level is always high, because so much of my mind is somewhere else altogether. At times, this can bring on a blessed kind of tunnel vision, where all worries that aren’t the book fall away for a while; at other times, all it does is make me more likely to walk into both literal and metaphorical walls.
Good luck with this one. I know exactly how you feel cos I’m near the end of my novel too and had to go back and fix umpteen scenes.