Inquiring about prop firm payouts and liquidity reliability

I'm currently looking for a new prop firm. Many offer good conditions, but my main concern is the backend infrastructure, specifically the payout system and the liquidity of the brokers they use. I've experienced delayed payouts for no reason, or during volatile markets, my orders were frequently rejected due to insufficient liquidity or spreads widening excessively. I'd like to know what experiences others have had in assessing these risks when choosing a prop firm.

How can we know if a prop firm truly uses brokers with good liquidity and if their system can efficiently handle withdrawals, rather than just looking good on the surface but having backend issues?