Significant hitch in PIE when unloading a sublevel via level streaming volume on Mac

This does NOT happen on Windows and is not a regression as it occurs in 4.14.3

1. Open QAGame on Mac
2. Add a Level Streaming Volume in front of the Player Start
3. Open the Levels tab under Window
4. Create a new sublevel
5. Place 2 Cones into the sublevel and save it
6. Open the sublevel's details window
7. Click the + button next to streaming volumes
8. Select the level streaming volume from the dropdown
9. PIE and move into the level streaming volume
10. Move out of the level streaming volume

Result: A hitch can be noticed when the level is unloaded

Expected: level is smoothly unloaded.