UActorComponent::RegisterComponentWithWorld() does not have a check for bAutoRegister near the end of the function, where it registers the component's children if it was created by the Construction Script. This can cause children that have bAutoRegister set to false to be registered when they are not meant to be.
Regression?: No
None - Source code issue
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-52878 in the post.