Steps to repro:

1. Open attached project and '1_SpeedTree_Customization' scenes;
2. Scroll in and out to invoke SpeedTree transition between billboard and LOD3.

Expected result:
Transition goes smoothly for all tree billboards.

Actual result:
Blinking artifact is shown when billboard transitions to LOD in case when multiple billboards overlap each other. See attached video.

Notes:
- Reproducible in 2017.2.0a1, 2017.1.0b8, 5.6.1p2;
- Reproducible on Windows 10 and OSX 10.12.5;
- Not reproducible for promitive LOD group or single tree; reproducible only when at least 2 tree billboards ovelap each other;
- Not reproducible when cross-fade animation is off;
- Reproducible in both Editor and Standalone player.