I've been messing around with the glitter effect  but I'm getting a bug where glitter is being applied to the whole skin. Has anyone else run into this?

For the most part the glitter sticks to the grayscale map I give as the sfx map. It just also seems to apply a super subtle glitter to the entire model. The lighter parts of my sfx map produce the most glitter but I have large parts that are completely black, which shouldn't have any sfx, but glitter is still showing up in those areas. 

I've tried redoing my sfx map to make sure the black parts are fully black and adding/removing the alpha channel. And the issue still persists. Maybe I'm doing something wrong or misunderstanding how the sfx works but I dont think so. If I turn the glitter off and turn the iridescent effect on, the full black parts of my sfx map don't have any iridescence to them. Same with the pearlescent effect, only the glitter shows up where it shouldn't. Lastly, I also use the overlay feature to cover up the pattern on certain parts of the model. That works like I expect, completely covering the regular albedo and the iridescent and pearlescent effects but seems to make the bugged background glitter be even more visible. The attached picture is one of those areas where I'm covering up the albedo with the overlay and it's making the glitter(that shouldn't be there to begin with) stand out. 

Sorry for the essay, any help/advice is appreciated.

If this is a bug, is there a specific place I can report it to Valve or should I just contact Steam support? 

A glitter bug? Or am I doing something wrong?