LevelScriptActor can be destroyed from a channel close on the client before the associated level is removed from the world, which prevents proper cleanup of the network driver. We should look into making them 'no delete' similar to the persistent level's WorldSettings, since they are placed static actors and the level could be reloaded on the client for re-use.
See associated UDN thread.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-64195 in the post.