Phantom I stereo issue

[Jann]

The solution to my crackling/drop-outs/sync issues was using an ethernet cable between the two speakers.

This way it's always been super stable, can only recommend. @ragwo pointed this already out, but I think it has been overseen.

Another way to test whether it's your networks fault or the speakers fault is to connect the speakers via Toslink to a TV/PC/Mac. If the two speakers are then connected through ethernet with each other, the setup should be immune to network related issues and one can find out if the speakers are working fine...