I still have a problems since the last 3-4 releases ago. SOmetimes when leave wifi, i will have limited connection to internet. For example i receive messages to Whatsapp, but no pictures or videos. You tube says i am not conected to internet, but i see the 4G icon and the UL DL arrows. In order to make the internet work again, I have to go to SIM card settings/Preferred Network Type and change from GSM/WCDMA/LTE to TD-SCDMA/GSM/WCDMA/LTE. What is happening????? And after i have the problem again, ...i switch from TD-SCDMA/GSM/WCDMA/LTE to GSM/WCDMA/LTE...and it works again. Or just restart the phone.
That's very similar to the problem I have with my Mi Mix 2S ...