Why is it so difficult to print metallic gold ink on a navy blue substrate?
Gold is a warmer color, meaning the hue is more red than blue. So if the gold allows one speck of the navy to show through it goes from gold to oxidized brass which results in a tarnished.
To ensure that you don't get any show through, take the mesh count you are using now and swap it for a mesh with the same thread diameter but a couple counts less. For example, if you use a 156/48, instead go for a 137/48 so you have a lower count/higher volume mesh. Then, use a polymer fill-blade and a bi-axial print blade, set the fill to zero angle and use sufficient pressure so you have a thin but opaque layer of gold after the fill stroke. Set the biaxial print blade to 5 degrees with only enough pressure to clean the non-image areas and clear the openings. Finally, run both fill and print blades at maximum stroke speed. This should provide you with enough coverage for a vibrant, bright gold.