Are you sure your character doesn’t have 2 collision meshes on them? Is there only a capsule or do you have more components in there? Maybe the character skelMesh and the Capsule collide?.. I am creating a side scroller game too and it works fine for me, my character has no collision , only the Capsule does that.
You could also make a work around, you could make a bool variable so that after the first time it is overlapped you’d make it so that second overlap doesn’t do anything in your event graph.