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Thank you so much, it's working now. Now I feel dumb for not seeing this obvious error :-D

If I may add. If the forget logic is run through, it looks like this. Flow is green, the list that is returned is purple and the list that is supposed to be returned is not used.

Hi Lazlo,

Thank you so much for your answer. I checked again what you said, but that doesn't seem to be the problem. However, I noticed something. In the screenshot below you can see the Super Unit I created to add or remove the colliders to the list. At the beginning of the game the list is always empty. Then a collider is added (via OnCollisionEnter). This works quite well so far. But if OnCollisionExit is triggered, it runs through the lower (blue) part of the flow graph (which is correct), but returns the list of the upper (red) part "Remember / Add to List logic" instead of the list that I have linked. So the flow is correct, but it returns the wrong list. It also explains why there is a problem with the returned list of AddItem. It tries to return the result of AddList. But when performing the "Forget"-logic the function AddItem is never called.

Is it a problem that I have so many different output nodes? I hope my problem is understandable. Many thanks in advance!