Hello Everyone,
As many of you have pointed out, this issue is caused by the use of Child Actor Components. As emretanirgan pointed out, this crash was reported and has been fixed for 4.15: Unreal Engine Issues and Bug Tracker (UE-39323) . You can check the 4.15 branch on GitHub to see if the issues still occurs for you there. For the time being, the best solution would be to avoid the use of child actor components. If you are still getting a crash after the final release of 4.15, feel free to comment back here to reopen this post for further investigation.
Cheers