Expanding spheres inside a game engine doesn’t have the logical effect you’d expect.
What the game engine does is that when it expands the sphere, it doesn’t take into account any assets that might be “Pushed Away”. It will continue to grow and “Overlap” actors and meshes rather than applying the expected effect.
Thankfully this can completed using a simple equation. When your growing sphere overlaps an actor, filter out any actors you’d like to physically push via Tags, and then use the “Unscaled Radius” of the sphere to move actors directly away from the radius equal to the amount the sphere grew on that tick.
Overlapped Actor > Actor has Correct tag > Move actor X Distance directly away from the sphere.
X = Amount the radius grew this tick.
This system is already automated inside of Ue4 when moving the location of actors, but not scaling. I imagine they will change this in future, but for now, you’re better off utilizing this method, or one similar.