I can totally relate to the bug, it happened to me in January during the Global Game Jam, we had very little time and used unity to make the game and this occurred to the leaves in the background. Of course we had no idea why or how did this happen but in the end I forgot to point out the little bug.

Still image from the video:

Hình ảnh bị xóa do không hỗ trợ HTTPS. | Vẫn hiển thị

Observable video:

Source files: http://globalgamejam.org/2016/games/spinder http://ggj.s3.amazonaws.com/games/2016/01/31/1956/GGJ2016.zip

Hello! I know you may not be the most comfortable with english but this is supposed to explain part of the problem: Premultiply Alpha

In short:
If you use Spine/Skeleton shader or any premultiply alpha shader, you need to follow the recommended export settings.
If you use Sprite/Default or any straight alpha shader, you need to UNCHECK Premultiply Alpha.

Oooh so that's why!!O: Thank you Pharan!