Connect a standalone WiFi router people! It fixed all my problems!
The all-in-one Comcast gateways are absolute junk with WiFi. Buy a router with big antennas, put it prominently on a shelf centrally located in your house (not on the floor in a corner).
Most "internet" problems are actually WiFi problems. Comcast wont admit this because they want you to pay the monthly fee for their Gateways rather than buying your own modem and router.