random muting when listening to online radio

[AC Question]

Samsung Note 4 Edge. Purchased one year ago. When listening to online radio though 4 different apps, the phone self mutes and the volume cannot be turned up. This happens from 5 minutes to 4 hours of listening and is totally random. The only way to recover is to restart the device. Then it happens again. No new apps installed. No new programs installed. Been using the same apps for over a year. Just started 2 days ago. Checked the software update and it is up-to-date already. Android version 5.1.1