I have an old (2015) Arris Surfboard SBG6782-AC cable modem with wi-fi. Never had problem with Wi-fi dropping until recently. Happens to both of our phones intermittently and randomly. The only issue it is my cable modem, not Xfinity's. I can't understand why it would suddenly start dropping wi-fi. Wired signal (to computer) works 100% of the time. I have tried signal booster with no help. Any ideas (other than renting a new one from Xfinity)?