When using a Game instance to modify the sound in the editor the sound will ignore settings made by game instance. This issue appears to be occurring only in the editor, as running the game in standalone and packaged does not cause this issue. The user who reported this mentions that the audio device is created after the GameInstance is initialized.
There is a current workaround for the issue, which is to set a delay in the game instance.
This issue occurs in the 4.15.3 and 4.16 binary builds of the engine
Result: The Sound loops
Expected Result: The sound should fade after 1 second
Head over to the existing Questions & Answers thread and let us know what's up.