As I wrote on another thread, initial reception to my second book indicates there are problems with the first half - say around 70k words. (It dragged.) I am currently planning to rewrite it. And since it is the first half, the core of the plot must remain in place in order that the second half, which was received very well, can remain in place.
I think your description of "burn down" applies here quite well, because my current intention is to change almost nothing about what happens, but to change only how it is told and perhaps the timing and emphasis of certain elements. As much as I dislike what I see as rote rules about "conflict" etc., I suspect that something like that is what I got wrong - I prefer the word tension, because I don't think conflict is all that apt.
I'm so new to all this that I can't say how often it is likely to happen to me, I'd like to think I will learn from this experience and it will never happen again, but from the way I write (a mostly very vague outline), the chances are it will come up again ... and I accept that as part of the process. Curiously enough it was this first half for which I had the most detailed outline, I really don't seem to work well from such details - just hoping I can overcome this handicap for the re-write, yet another learning experience for me (got to be philosophical about it).