I have a Virgin router (Modem only mode), connected to a Asus Router and connected to this is Deco X20 of which i have three around the house

Issues i am having, my work laptop connects to the system via VPN using Cisco AnyConnect.  If i connect using the Deco Wifi SSN, i get dropouts at random intervals where i have to restart the computer to connect.  Also happens when i connect via Ethernet to the X20 node located in my office.  Same is happening to my wife's work computer but their connection system is a bit different but from what i can guess at, its via a VPN gateway as well.

Xbox is also showing as an issue with Double NAT.  I am guessing this is potentially the issue that may solve all issues.  I have heard port-forwarding mentioned as well and i don't really know which point to start with because i feel all of them will 'work' but i just need a solution process that will solve our issues

TIA