I'm having similar problems. I have several apps that wont load data correctly on WIFI, but work as son as the WIFI is stopped. But all the time basic internet connectivity (Chrome, etc) is fine. Example apps are:
Weather - will not refresh
Flight Radar 24 - will not load aircraft (spinning wheel) but does load maps
BBC Sounds - does not load content, My Sounds, etc
It will often work for an hour or so if there is a significant network change (bounce router, reset connect network on phone), but then stop again. Very annoying to have to keep dropping wifi.