Hey Joseph,
Glad to hear you're using WAG for your demo-reel :)
Hmm... Sounds really strange with the inconsistency. How did you implement the music? Did you use the predefined Music_Enemies Event? If so, have you made sure that the Music Segments are exactly the same length as the Music_Region Music Segments? I'm asking because the region music is set up to call the enemy music each time it loops. There's more about that here: https://www.audiokinetic.com/courses/wwise301/?source=wwise301&id=Synchronizing_Music_Systems#read
Otherwise, you can try to set the enemy music to loop, then reset the Wwise-Type 'Enemy Music Event" property located the Managers game object > GameManager script, and finally, add an AkEvent on the Manager game object (set it to trigger on Start) and select the Music_Enemies Event there. This way, the region music would not be posting the enemy music from the GameManager automatically, but instead, you would be posting the Event separately.
Hope this helps! Let us know whether this helps