Unable to varnish Vallejo Liquid Old Gold - Help

Hey, I hope this is the right place to ask.

I'm currently in the process of airbrushing the Volks 1/100 Knight of Gold using Vallejo Liquid Gold paints (old Gold & Copper) on top of Vallejo Gloss Black primer.

The paints themselves go on perfectly smooth and flow through the airbrush nicely. However I'm running into issues when trying to varnish the Old Gold. No matter what varnish/mixture (using vallejo thinners/flow improvers etc. and alcohol or water) I use, it always beads up on the surface. I've tried to alter the pressure or to apply it in a mist or in multiple coats but I could never get it to settle smoothly. I've even tried to use Vallejo's clear primer to no avail.

None of the issues show up with the Liquid Gold Copper or Liquid Gold Gold paint from the exact same line of paints, which is the baffling part.

I'm really happy with the shine and shade of the Old Gold, so i'd be hesitant to change to a different paint.

So I'm looking for some advice on how I could go about varnishing the gold, because rn I feel like I've run out of ideas. Thanks