Reproduction steps:
1. Open the attached project "BugReport.zip";
2. Open the BugReport.unity scene;
3. Run the game.
4. Move the SpeedTree along the X Axis Or Y Axis in Scene window.

Expected results: the animation is applied normally, branches of the tree are moving naturally;
Actual results: branches begin to tremble.

Reproduced on: 5.3.5p8, 5.4.2f2, 5.5.0p2, 5.6.0b3.
Note: the attached video is showing the bug.

By Design: SpeedTree Wind animation is randomized by the position so that each tree can be animated differently.