Why won't my S5 pause the music on incoming texts?

[AC Question]

Hello everyone. I'm using an S5 running 6.0.1 Marshmallow. I play music through the headphone jack connected to a speaker. A phone call immediately pauses the music ringing from the phone. Conversely, an incoming text just lowers the music volume(causing missed texts). Recently upgraded from an S3, and it stopped every time. Exactly the opposite complaint from others here, I need to turn this feature ON. I've cleared the cache partition. What else can I try?