Audio cues not working when app is in the background

I have a iOS/watchOS app that gives audio cues, like a metronome, on specific patterns. The intent of the watch app is to have it at the same time as a workout app (ie Strava, Apple Fitness) and/or a music app (Spotify/Apple Music). The app works in the foreground just fine. But if I start another app (i.e. Strava) the haptic feedback and a "ding" continues to play in the background, but the "beep or voice" stops. Beep/voice works fine in iOS when in the background, just not in watchOS.

Audio cues not working when app is in the background
 
 
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