-For iPhone 6S and older, hold down the Home button (round button under screen) and the lock button (the button you use to turn off the screen) at the same time for about 10 seconds until you see the Apple logo. Let go of the buttons when you see the logo.
-For iPhone 7 and newer, unplug your phone if it’s charging. Power off the phone (7 and 8, hold down the lock button until you see “Slide to power off”. To shut down the iPhone X, quickly press and release the Volume Up button, then the Volume Down button, then press and hold the Side button. Your phone will show a “slide to power off” bar at the top. Slide that, and it will turn off your phone.) Leave it powered off for at least 60 seconds. Plug it in to a charger. Should see the Apple logo appear on the screen.
I did this method yesterday and haven’t had any weird audio interruptions since, though no guarantee that it’ll be permanent.
I have the same problem (iPhone 7p, Spotify premium), it seems like it is actually a problem on Snapchat's behalf. To temporarily fix it, I've turned off the notification sound in settings. For IOS, go to settings - notifications - Snapchat - sounds - select/swipe them off. You'll still receive your notifications, you just won't hear the sound. This will prevent music from stopping with every snap, but it may not prevent it from stopping while opening the app or a message/story.
Everybody experiencing this problem needs to go on the Apple website and have a 5 minute conversation with one of the “Genius’” who will file a report. The more reports they receive they will try to fix. This is not a snapchat problem - it is definitely an IOS issue