Without more info it is hard to pin down render issues just from looking at a render.  But in this case I believe the black spots are from not enough max transparency bounces. Try increasing the maximum number of bounces until it renders properly. It doesn't hurt to have the max set higher than you actually need either. To explain why you got what you posted in the first render. Superfly defaults to black if it runs out of transparency steps. This can be handled in a few different ways, Max bounces, shaders that default to transparent when running out of trans bounces, etc.... Turning the max up is far easier than the other routes....

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