Due diligence on payout reliability - what metrics do you track beyond the headline?

Been thinking a lot about payout reliability recently, especially with some of the recent volatility. Beyond just checking for on-time payments, what specific metrics or red flags do you seasoned folks look for when evaluating a broker's or PSP's ability to actually pay out, particularly for larger sums or during periods of high market stress? I'm talking about things that might not be immediately obvious, like their underlying banking relationships or liquidity providers, not just their advertised processing times. It's easy to get caught up in spreads, but if you can't access your capital reliably, that's a whole different ballgame. Always keen to hear how others approach this critical aspect of due diligence.