AVAudioPlayer/SKAudioNode audio no longer plays after interruption

Hi 👋! We have a SpriteKit-based app where we play AVAudio sounds in three different ways:

1. Effects (incl. UI sounds) with AVAudioPlayer.
2. Long looping tracks with AVAudioPlayer.
3. Short animation effects on the timeline of SpriteKit's SKScene files (effectively SKAudioNode nodes).

We've found that when you exit the app or otherwise interrupt audio plays, future audio plays often fail. For example, there's a WebKit-based video trailer inside the app, and if you play it, our looping background music track (2.) will stop playing, and won't resume as you close the trailer (return from WebKit). This is probably due to us not manually restarting the track (so may well be easily fixed). Periodically played AVAudioPlayer audio (1.) are not affected.

However, the more concerning thing is that the audio tracks on SKScene file timelines (3.) will no longer play. My hypothesis is that AVAudioEngine gets interrupted, and needs to be restarted for those AVAudioNode elements to regain functionality. Thing is, we don't deal with AVAudioEngine at all currently in the app, meaning it is never initiated to begin with.

Obviously things return to normal when you remove the app from short-term memory and restart it. However, it seems many of our users aren't doing this, and often report audio failing presumably due to some interruption in the past without the app ever being cleared from memory.

Any idea why timeline-run SKAudioNodes would fail like this? Should the app react to app backgrounding/foregrounding regarding audio?

Any help would be very much appreciated ✌️!