Prop Firm Payouts: Are Brokers & PSPs the Real Bottleneck?

Been thinking a lot about the whole prop firm payout process lately, specifically the last mile. It seems like a recurring theme across various firms that the actual transfer of funds, once approved, can be a pain point. We talk a lot about if a prop firm pays, but less about how smoothly they pay, and the underlying infrastructure.

Is the friction primarily on the prop firm's side, perhaps due to internal processes or their choice of payment service providers (PSPs)? Or is it more about the brokers they use for their pooled accounts and the ease (or lack thereof) with which funds can be disbursed to individual traders? Seems like KYC/AML on the PSP side can be a serious bottleneck too, especially with higher payout requests. Has anyone seen significant differences in payout speed/reliability between prop firms that use different brokers or PSPs? Just trying to identify where the weakest links typically lie in the chain.