I can’t call it an answer (and so I won’t post it as one) but I was having terrible, corrupted-style crashes this morning in 4.14 with child actors too. I had two instances of a child actor on a parent blueprint, and had one variable (an enum state) that I was changing in the dropdown properties. It would work fine until I shut down and reopened the editor - at which point it would immediately crash as soon as either the child actor, or the parent actor, (or the level that contained instances of the parent actor) were loaded.
If I went into the asset folder and moved the child actor asset out of the folder, I was then able to open the project and level - the parent object having lost its reference to the class of the child actor. Obviously, this mucked up a fair bit of my blueprint references.
What I did, was change the child actor to instead be an actor that was spawned on beginplay, with the enum variable changed as soon as it was spawned and attached.
The rest of the blueprints (once tidied up and converted to use the spawned version instead of the child-actor version) works fine, even after reopening the editor.
Hope all that is of useful reference to anyone else who may come across this issue! (It’s not an answer, but it may be useful data.)