I’m going to assume its happening twice without a break statement. Imagine you have two circles that intersect each other. They will share two points, if it isn’t the edge case. In the 3D case you will get a surface overlap, but it will just be points if you are dealing with unfilled volumes.
I very much recommend drawing the sphere with DrawDebugSphere() from “DrawDebugHelpers.h”. You will see the overlap points. Then post the picture. Text output is useful, but it really helps to see the traces.