Music loop cutting out in build

Question

Running into something strange I haven't seen before.
I have some music loops in a playlist which play accurately in wwise, accurately when playing in Unreal editor and in an editor build, but as soon as the music is in a full dev build the loops start to cut out.
Strangely they're cutting at the end of the track before rather than being delayed or cutting the start of the new track.
I have the music set to stream, zero latency and with a prefetch of 300ms.
Interestingly when I increase the prefetch value the drop out in music seems to correlate with the value of ms I put in here. So 1000 ms = a second drop out.
Seems almost like the initialising of the next track in memory is stopping the current track from playing.
I'm not getting any errors in the profiler when this happens.
Has anyone experienced this before? Could it be an issue with how the build is accessing the streamed audio vs audio in memory?