Whenever I had this, I used to go straight to the basics and ask myself:
1. What's happening in previous chapters (in one line)
2. What should happen next, logically, so that the characters can enter the scene of my last chapter.
First, I divide my story into a very, very basic layout of the beginning, the hotchpotch in the middle and the BAM ending. It's so basic that I leave the middle section with a single "She's gonna investigate what's happening" and move on to the end. The problem usually arises in the hotchpotch in the middle. So, I turn that into a very basic flowchart that shows me how I'm gonna lead the character step by step with her actions/ new discoveries and new challenges during her investigation until she meets the end. It's super basic, I don't go into the nitty gritty details of how she will react with words or expressions or whatever.
Usually I find that I'm stuck in that flowchart. And that happens because of a lack of idea on:
1. How they will act.
2. What problems they will face because of their previous actions/ creating an arc that's new but relevant to the ending.
For one, I look into the character's personality and let them decide what they will do. (If reckless: dives into a problem. If cautious: lays back and lets others mess the story up)
For the second problem, I look into the same sources that started my imagination in the first place, be it a few mangas of the same genre or a movie or a novel. Usually, my mind starts getting a few ideas again and I enter it in the flowchart, not the actual story.
Edit: What I mean is, the more you're stuck, the broader you should make your flowchart. Something like: Y is stuck in a scene A. Prota needs to save Y. Should prota go to the scene of action (A) / not go? Yeah. That basic.
Only when I'm entirely done with the flowchart, I subdivide it into sub-flowcharts where I take into account the responses of each character to the situation, the loopholes that I'd left open in the previous chapters and the single-chapter-plot. Often that builds up a lot of content. And then, I start writing the chapters one by one by putting the entries in the flowchart.
I wouldn't know about you all but it has worked for me so far. Hope this helps, friend.