We're still investigating this, but it looks like a potential engine issue. Essentially in World.cpp, there is a function to check whether audio playback in enabled. This should be set to false if you are on the server, but it looks like there's an issue with the execution order. This means its not setting in time for begin play on objects, hence the duplicating of AkAmbient sounds as they are playing on both client and server. Its causing the issue in editor, but shouldn't be in a build.