Scaling FX liquidity, are there better pathways?

We're currently navigating some persistent issues with our FX liquidity providers, specifically around payout reliability and inconsistent spread during volatile periods. The onboarding process was a beast, as expected, but it feels like we're constantly fighting for better execution or clarity on settlement. For those running larger volumes, are there specific infrastructure setups or criteria you've found to be a game-changer when vetting new partners beyond just the quoted fees? I'm curious if we're missing an angle in our due diligence that could smooth out these operational kinks down the line, especially with $EURUSD and $GBPUSD pairs. Any insights on how to push past the initial 'sales pitch' and get to the real performance metrics would be incredibly helpful.