In UE 4.14, we’ve been getting the similar problem for the past week. It crashes when opening the asset in the editor. In code, it crashes in:
ChildActorComponent::Serialize()
It CastChecks the ChildActorTemplate to an Actor (line 93), which fails. The ChildActorTemplate is not null.
If I change the CastCheck to a simple Cast (if it succeeds) it seems to fix the problem at least on our build. I don’t know enough about the serialization or the actortemplates to know if that’s going to cause problems elsewhere, though.