Power Supply only boots after days of sitting unplugged

Hello! I have a Cosair CX500M that is having issues booting a PC. The system will always turn on (HDD, GPU, fans, etc.) but nothing will initialize. When the system will boot successfully, the CPU fan immediately spins up faster than it would when my PSU is having this problem. If I allows the PSU to sit unplugged for a few days it will boot up 100% of the time and remain on for days without issue. If the system shuts off and attempts to power back on it will not work. I suspect that it only boots when the capacitors are fully discharged (or close to it) and otherwise the motherboard is not receiving the Power Good Signal.

My question is, how can I quickly drain the capacitors? I saw a guide here on IFixIt about building a capacitor discharge tool, but I’m not sure how to use it. I have tried grounding the PS_ON pin for awhile (just using a bent paper clip) and that didn’t help. Any ideas?

And no, I don’t want to replace the PSU. I’m just using it in a test system and don’t really care if I break something.