Have you tried to make the trigger box into its own blueprint and have it trigger through that instead of the level blueprint?
Go to your blueprints folder, right-click and select to create a Blueprint asset. Click on All Classes and type in “TriggerBox.” Name it whatever you would like. Then put in the blueprints shown in this image:
This basically says, “Hey, I overlapped with an actor, so once and only once I’ll get all the matinee actors and look at their names and if they name of the matinee actor is the one I know, I’ll play it.” You can name your MatineeActor whatever, I just kept the default since I was only making an example. I wouldn’t be surprised if there are better practices for this, but this is quick and gets you the result you want. You could even make a variable called “MatineeName” and have it be editable/public so you can edit the name in Details from the main level viewport when you place the trigger actor. To do that you’d just right click the pink input node in the String Equals and promote it to a variable, then in the left hand side click the closed eye symbol. Now when you look at your custom trigger box you can see the MatineeName variable is editable so you can trigger a different matinee actor with it. (I added a light so I knew where to step.)
