This issue has been closed as 'Won't Fix' due to an extended period of time without updates. If this issue is important to you please let us know by posting on the AnswerHub or UDN, and Epic will re-open the ticket for further review.
When a new client joins a server all of the actors will be replaced with new copies of themselves. This will cause things like the construction script and event begin play nodes to fire off every time a client joins a sever even though the level is already up and running.
Head over to the existing Questions & Answers thread and let us know what's up.