Call me silly if you want, I can handle it....   but are you sure these dots are not just the way your image editing tool (whatever it is) shows transparency? Photoshop uses a checkerboard pattern.

In other words, are you sure these dots are in the render itself, and not just in the way it is being displayed here?

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)