Share your experience!
Since the Last update from Sony (marshmallow) video calls with Line app always broke without earphone !!!
I had tried :
1. Reset the app. Go to Settings > Apps > [Problem App] > Storage > Clear Data, then restart my phone.
2. Uninstall and reinstall the latest version of the app in the Google Play Store.
= Same problem, so I tried :
1. Disable the noise supression option in call
2. Reset the app. Go to Settings > Apps > [Problem App] > Storage > Clear Data, then restart my phone.
3. Uninstall and reinstall the latest version of the app in the Google Play Store.
= Same problem !
Sony drives me crazy !!! (with earphone all it's okay but I don't have always on me...)
That's something that the Line developers have to address as this is a third party app.
I wrote the same message to Line Support...
Wait and see...
Just think about it, if you have any issues with the facebook app or whatsapp or chrome or clash royale or pokemon go or Gmail, it will be up to the app/game developers to address any issue not Sony, the same goes for iOS and other Android brands.
haha, I understand, so my next phone will be a Samsung !! 
Lol, it'll be the same with Samsung if there's an issue with the app, either or, enjoy your next phone but do let us know what Line say about this bug.