Problems with Some Apps on Xfinity Wifi

For the last few months I have had problems with certain apps across several devices (TV, Android, etc.) not working while on wifi. Some will not open or will take minutes to open. Examples: ESPN app on phone, many, many streaming apps on TV. If I turn on data they work fine, if I am on a different wifi system they work fine. Multiple attempts to resolve with Xfinity techs, including having the router replaced. Download speeds are fine, wifi is functioning properly according to techs.

There are two similar posts here: https://forums.xfinity.com/conversations/your-home-network/problems-with-certain-apps-on-xfinity-wifi/62d597c3c1d78836ea3eba24

https://forums.xfinity.com/conversations/your-home-network/xfinity-wifi-not-connecting-to-certain-apps/627d29b96176867c2ed319c0

I'm looking for suggestions that do not involve upgrading or getting new equipment. This issue is brand new and the WiFi worked universally for over a year. Please help!