How to stop character movement during a cutscene?

The way you described this seems to be more of an animation issue than a character movement issue.

I’d say this is a very specific matter as I can’t know how your character is programmed and animated, but I could try to list a possible step-by-step on how to find this though:

  1. Open your character’s animation blueprint (If you can’t find it, you can locate it by selecting the “Mesh” component in you character’s blueprint, and in the details panel look for Animation->Anim Class and click on the magnifier icon to locate it in the asset browser)
  2. Inside the animation blueprint you have two graphs: EventGraph and AnimGraph. Open the AnimGraph, this is where your animation is defined. It is usually defined with a single state machine, if it is so, double click to open it. If it is not, you’d have to interpret it and open everything to find where your “Running” animation is defined and what variable controls it.
  3. Now open the EventGraph in your animation blueprint and try to find where the variable that controls your “Running” animation set true/false (if its a boolean) or where “Speed” is calculated in case it uses a BlendSpace (BlendSpace is essentially a way to “Mix” two animations so you can have a haf-way animations between idle and walk instead of a boolean IsWalking or not)
  4. Now its up to you: find any logic errors of why your running variable is not being properly set to 0 when you tell your character to stop. I can’t tell you what exactly the error is because I can’t see your code. Maybe some screenshots would help me to help you figure out what it is.

Best of luck,
Cassio