Oh sorry to hear that - are you on iOS or Android?
One thing we do know to be an issue is that sometimes if the offline library cache gets too big it can affect offline playback.
In 1.1.16 which just went live today we've introduced a storage manager that lets you view and clear specific offline caches like audio / images / library etc.
Can you try updating to this version, clearing your library cache from the storage settings page, and see if that resolves the issue for you?
If not please can you send me an email oscar at fountain.fm and I'll investigate further.
