apps running super slow or not at all on android phone connected to wifi

2 weeks ago, we had xfinity installed in our house.  The modem that was mailed was the Arris Model TG1682G.  After the technician left, I noticed I couldn't open the Xfinity ap on my Samsung Galaxy phone while connected to wifi.  It would have a white screen with 3 dots in a circle.  When I would turn my wifi on my phone off, it connected right away.  This was the case with my Arlo ap (security cameras - videos would just buffer), Ring Doorbell ap - videos would not play, the Weather ap.  All worked fine on iphone and ipads.   And all would pop right up when I turned wifi off.  Netflix, Hulu, FB and many other aps ran just fine.  After countless hours chatting with Xfinity assistant (HATE THAT), dividing my network to 2.4 and 5, talking to a technical rep for hours, resetting the modem, powering down my phone, and searching the forums (many other posts confirmed my issue), they agreed to send a technician out.  He got here and promptly told us that the modem was 4 generations old and replaced it with a newer modem Technicolor CGM4140COM revision 2.0.  SOLVED ALL THE PROBLEMS INSTANTLY.  Hope this helps others with the same issue.  Obviously, Xfinity is deploying old technology out of their warehouses and the techs have up to date equipment.