Same thing happens to my iPad. It was doing it way before any if the resent updates. I think it's an iPad bug not a DF bug. The pad thinks the headphones are plugged in. Buddy of mine says its the headphone jack. Needs replaced. He is a tech nut. He rebuilds phones/computers/iPads and things of that sort. My sound seems to go when my pad gets real warm.
Resetting the pad doesn't work, nothing does. Sometimes it lasts a few days, sometimes a few games, sometimes a few minutes.
I bought a set of Bluetooth head phones. I can't stand to have them on. It works though.
Best thing I found was a Bluetooth speaker. No wires and I still have sound. It's still a pain in the rump.
I play a while with the speaker until my sound returns. I hard reset the pad every time I turn it off.