The Linksys EA 8350 is a very powerful DUAL frequency router capable of providing high speed access to any WiFi device within 100 feet of the router. My guess is that your system is having a very bad WiFi connection conflict.
If this were my system, I would turn off all other WiFi extenders - You don't need them! Next shutdown ALL cameras and reconfigure them one-by-one to use the 5 GHz band if possible. Give each camera it's own STATIC IP address on both the camera and router tables and reboot each camera one-by-one to bring them online. If you want to use Auto DHCP then be sure the cameras don't have conflicting static IP addresses already coded in their internal table. Be sure the router CHANNEL WIDTH for the 5 GHz is set to max 80 MHz.
Connect your laptop or and other device to the 2.4 GHz band.