Hey TheJamsh, I made the change to make AttachmentReplication private. There were some good reasons, namely that with it being public some people were trying to set values on it directly thinking that would actually have an effect on the replication, when in fact GatherCurrentMovement() is all that matters. I just added a comment to make this more clear.
Another important reason is that SceneComponent used to fill in AttachComponent and AttachSocket, but that has been refactored to just happen in Actor now as well. In your example override, you don’t fill in these variables, so you might have an error there. I think in your case though you can still use the Super implementation in place of the block where you fill in AttachmentReplication. Unless the root component is simulating physics (when AttachmentReplication wouldn’t be used anyway), this should result in the correct behavior (plus correctly set the aforementioned variables).
As for the DOREPLIFETIME macros etc… that is an unfortunate side effect that we are thinking about how to address. I believe it comes from the GET_MEMBER_NAME_CHECKED macro used by the network replication macros. While it might be possible to make AttachmentReplication protected (I’d like input on this), the macros will still have this issue.