About three months ago I suggested that I had taken a wrong turning in the novel and had somehow let it reach a climax about 25,000 words short of the projected end. At the time I thought I could tweak what I had already written to shift the climax towards the end. Since then I have struggled to make any progress at all on the final chapters.
My failure to get anywhere makes me think I was wrong to stick with the novel outline in the face of compelling evidence that I had actually reached the natural endpoint of the story. So I have decided simply to discard the final part. I still have some tweaking to do, of course. In particular, the chapters that now end the story were not written as a conclusion, so I need to rewrite them to tie up loose ends properly. I also need to give one of the minor characters, who turns out to play a crucial role in the climax, a voice of his own, which will involve slipping into the story several scenes from his point of view.
This means that I have more or less finished the novel!