Certain Apps don't remember sound notification changes

Hi,

I'm really struggling with my Galaxy s7 edge - with a really annoying issue, where a number of apps (Twitter, Android authority, BBC sport) - not all apps will not remember the change I've made to the notification sound. It just defaults back to the default sound. I've seen a number of posts on various forums relating to Twitter, but in my experience, its not just twitter.

Anybody got a resolution?

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