@Tiberius777,

From what it sounds like, you are running two routers on one network, which will often cause conflicts and stability issues. If your Deco Network are Downstream from your router, then the Deco nodes need to either be set up in Access Point Mode, or your xfinity device needs to be placed in Bridge/IP Passthrough Mode. Placing the devices in AP mode will cause the devices to work as an extension of your Xfininty network,  while Router Mode will provide all features and will create/manage its own network.

The easiest solution is to place the Decos in AP Mode, however many of the mesh and management features will then be lost.