Audio and mic is gone when alarm is trigger

While you are in video call, if the iPhone alarm is triggered, all of sudden you cannot hear any sounds from your friend, and your friend cannot hear you anymore either.
If then you click on the alarm notification to navigate to clock app, and come back to line app, it will cut the video call...
please fix this annoying bug because it has been there for long long time...

ECispissedOFF about LINE, v7.5.1