I'm not sure how common this is, but it seems like every time I hit around page two hundred or two-twenty I also hit this strange, surreal slump that seems to persist until I force myself to take a day or two break from my work. I think part of it is seeing that speck of light peeking in from the end of the tunnel, and another likely factor is that small sense of burn-out that comes with working and perfecting one storyline for months straight, knowing just how much work the hundred or so remaining pages might be ... hoping that the last third of the story will live up to the first two.
All that a writer must do to lead up to a good climax and conclusion really can be draining ... physically, mentally, and sometimes even psychologically and spiritually. It can be every bit as difficult as finding just the right text for that first empty page of Chapter One. Endings are easy to rush, and a rushed ending is never any good. I've taken more than one approach in working to solve this issue in my own writing. Sometimes I find it easier simply to go with the impulse to rush through to the end, and then go back through it, a week or two later, with a red marker and a fresh approach. When I have the energy, and the Muses are also feeling particularly helpful, I literally force myself to take my time. If I'm tired, I force myself to take a break. This is not always easy, but I'm getting better at it.