@wertymole,

Is it possible you have set up a device white list or black list for your network security? 

The first thing I always recommend when disconnects like this happen is to navigate to the Wi-Fi settings on your iPhone and disable the setting on your home network for "Use Private Addressing" as this feature can cause issues and isn't as necessary for a home network.

Otherwise, I would ensure that the Deco S4 is updated with the latest firmware. Also, Does this happen with any of your other devices?

  @wertymole,

Going through some of our previous posts for apple iphones disconnecting from the network, points me to believe that the Fast Roaming option on the router, is what is causing the devices to disconnect. There is a great post on our EN forums regarding the feature and where it can be found in your settings:

 https://community.tp-link.com/en/home/forum/topic/180194

Make sure to come back to the US forums after visiting!