For me this crash occurs without any calls to the AddChildActorComponent node at all. I just have an Actor Blueprint set up with a lot of Child Actor Components in it that are other Actor Blueprints. The problem seems to happen when I try to get Child Actor from the Child Actor Component and cast it to its class, and then call a function in that blueprint class. I thought it was related to issue UE-38690 but I just built from source with that fix, recreated the blueprints that were having the issues, and I’m still getting the crash. The weird thing is that it’ll work fine for a bit, and at some point the Blueprint will get corrupted and I won’t be able to open the project again. The only way to get around it is to move the Blueprint out of the project folder, open up the project, and move it back in again, as one commenter mentioned. Let me know if I should open up a new bug report for this, but I figured the error was pretty similar. Here’s what I get:
[2016.12.04-22.22.52:633][ 0]LogWindows:Error: Fatal error: [File:C:\Users\Emre\Perforce\UnrealEngine-4.14\Engine\Source\Runtime\CoreUObject\Private\Templates\Casts.cpp] [Line: 11]
[2016.12.04-22.22.52:633][ 0]LogWindows:Error: Cast of LinkerPlaceholderExportObject /Game/Blueprints/UI/PD_HandMenu_BP.PD_HandMenu_BP_C:DrumsTab_GEN_VARIABLE.DrumsTab_GEN_VARIABLE_PD_BasicButton_BP_C_CAT to Actor failed