Hey Eliah -
Apologies for the delayed reply and sorry for the trouble. Thanks for sharing the solution as well!
I don't have a copy of Auria, unfortunately, but I'll see if I can track down the issue.
What sample rate are you using for Borderlands? It could be that Borderlands is running at 22050, and Auria expects 44100. You can adjust this value in the settings menu (gear icon) - just make sure you restart the app once you've changed to a different rate. The problem has to do with how iOS handles the system sample rate. Basically, the first app launched gets to set the global rate. The audio engine that Borderlands uses handles sample rate conversion relatively well, but there can be issues with launch order of apps (hence the solution that you found).
Best,
Chris