I have a polygon symbol I'm using with a marker symbol inside with a number (since key number labeling is never as good as one would like).
The symbol is, for some reason, transparent.

I have checked and there isn't any blending mode or transparency.

I can also confirm there isn't any transparency set to the symbol layer

Interestingly enough, the legend item is also transparent, including the stroke.

Can also confirm there isn't a difference between RGB and CMYK
What is going on here?