Mobile app fails to connect from remote location over WiFi

[olegos76]

Mobile phone at remote location (tried 3 different WiFi locations with all having different routers).
Connection attempt made through WiFi.

Result: almost 90% of the time the app will fail to connect (only Devices & empty Library tabs shown; Mode not showing up), in about 20 sec. the app throws me out and asks me to login again.
Workaround: force close it. Switch to 4G and try again. On 4G it may fail as well, but only fails 10% of time.

[jguerdat]

Reboot the phone and reinstall the app. What phone and OS?