SoundBank is unloaded after PostEvent and the sound stopped, how to prevent the sound from being stopped?

Question

I called the PostEvent() function to trigger a loop event, but a few moments later, the related SoundBank was unloaded automatically, so the sound was stopped too.

How to prevent the SoundBank from being unloaded? Is it possible to make the sound continue to play even if the SoundBank is unloaded?