Transparency where there should be none

I was playing with a close up view of a part that includes a clear housing.

Take a look at the attached image ....

This is the PNG file opened in Photoshop.

The final rendered image has areas of transparency on some of the surfaces of the clear housing. The parts within the housing and the parts behind should prevent any transparency from occurring given that there is no background visible.

The settings for the render were as follows..

Output size: 2200 x 1220

Format: PNG (not 16 bit)

Preview Quality: Good

Final Render Quality: Best

Gamma: 1.6

Bloom: OFF

Contour: OFF

Direct Caustics: OFF

Is there a setting I'm missing or do I need to be at Maximum final render quality?

I know I can put a white layer behind it in Photoshop, but I curious as to what caused it.

Thanks

SolidworksPhotoview 360