Vongrak
Most authors have said the same thing in their notes. There always seams to be a few chapters that just force their way into a story, but were completely unplanned, yet the story just doesn't work right without them. I've lost count of the number of author notes/foreword/byline/interview that mention this happening to them. As such, I wouldn't worry too much about it, so long as it doesn't derail the story your telling.