Hi Napoleon,
Okay, I was able to reproduce this in a new project. I think project I was testing on was converted up from 4.7.0 and then 4.7.1, so maybe this changed somewhere in there and converted projects don’t have this error? Anyway, I don’t know if it’s a bug. You’ll notice that if you drop Child BP into level and PIE, Event Begin Play inherited from Parent fires. It doesn’t show up in graph automatically, but if you right-click Event Begin Play node in Child and select Add Call to Parent Function, it will be there. Deleting it will remove that functionality from Child.
This seems inconsistent to me, since creating a new Child after change is made in Parent WILL display Parent function call automatically. I created a bug report (UE-11428) and I’ll let you know what developers say. In meantime, right-click Event nodes to Add Call to Parent Function to get that node in graph.
Hope that helps!