Please try clearing cache of the device to see if it helps. As a work-around please try enabling air plane mode and disabling airplane mode to see if it helps temporarily resolve the issue. If you are on ZTI7 software, please update to latest software ZTJ3. If issue happens on ZTJ3, as well, please send us an error report immediately after issue is observed with a video recording if possible. Are you observing any loss of mobile data once this happens?
One UI Beta Team.