Using 4.8.0 Preview 4 raises some issues with Overlapping events. It seems that default character controller (capsule shaped) intersecting with a Sphere Collision component (part of a custom Actor) raises enter/leave overlapping events every time character moves inside Sphere.
Is there anything of this sort in 4.8 release bug list? same code (using blueprints) worked in 4.7.6 correctly.