See UDN https://udn.unrealengine.com/questions/473245/attachcomponent-is-not-replicated-correctly-if-re.html
See: https://udn.unrealengine.com/questions/473245/attachcomponent-is-not-replicated-correctly-if-re.html
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-67510 in the post.