I'm having the same problem (https://community.tp-link.com/en/home/forum/topic/694398). When I set up a new AX53 router as a satellite, the main network is exposed, even though it's configured as hidden on the main router. I tested this by turning off the satellite router, and the main network is hidden, becoming exposed only when the AX53 is turned on. I've already reset both routers, and this behavior persists. Is there any way to force this synchronization between the master and satellite?