UE4 Undesirable Diffraction Results - What am I doing wrong? [closed]

Question

This video demonstrates my problem:
https://www.youtube.com/watch?v=DJ1KUA-18VE

The bright green sphere is the audio source. Diffraction seems to be working correctly in some scenarios, but stops working in other scenarios.
What causes this behavior? How can I prevent it from happening? I worry that if it gives undesirable results in a controlled, 'comfortable' scenario such as two straight corners, it might prove problematic in more complex scenarios.

Any help is much appreciated!

Comments

It's possible your listener is clipping through the geometry: this would be most evident in top-down view.