Hello. Transparency is hard to handle. Shapespark uses order dependent algorithm that requires rendering of triangles from the furthest away to the closest to the camera. Such sorting is not always possible, and the problems that you see are the result of incorrect render order.
Foliage textures use binary transparency: a pixel is either fully opaque or fully transparent. It is possible to detect such textures and handle them in a different way that does not require rendering from back to front. We will try to add such improvement in one of upcoming releases.