You suddenly realize you can fix it. The problem with That One Scene isn’t the events, nor the point of view; nor really the pacing. The problem is the feel–the taste left in the reader’s aural mouth at the end of it. You accidentally let slip an implication that one character is less concerned than you wanted her to be, or that another is distracted about whole ‘nother part of the book, or they’re failing to respond to something you were sure they had to respond to, so it just leaves a taste like a gin & tonic when the tonic’s gone flat. You don’t want that taste on the reader’s tongue going into the next scene, because at best it will knock the reader out of the story a bit, and at worst it will give the false impression that this is another kind of story altogether, leading to disappointment either now, or when it proves not to be.
You are pleased. Now you see the problem. Fixing that one thing in that one scene can redirect the entire book, and make the payoff feel like a payoff, the resolution feel like a resolution; it sets up the Happy Reader Sigh when the reader (slowly and a little regretfully) sets down the book and goes,”Yeah, that was a BOOK.”
Just that one scene can do it, and now you’ve spotted it. Now it is just a simple matter of fixing it by removing a couple of words. Or adding a couple. Or rewriting it with different characters or different events. Or changing everything in the book that leads up to it, and then everything that follows from it.
Well, thank Christ you’ve found it.
Best of luck with that.