Clean and DeOxit all connections.
This means everything. Any place where a wire is connected to something else (through a pin, terminal post, etc). I'm not familiar with that PS and what connections it has. But if wiggling wires changes things, you could very easily have a spot of oxide at some contact point, that you can't easily see.
You want to hit all contact points with something abrasive (fiberglass pen, Dremel wire wheel, 2000-grit sandpaper) to remove anything you can't see. Then DeOxit and reseat.
Sorry if it sounds simplistic, and is the same thing I say in many threads here. But oxidized contacts are responsible for a HUGE number of problems in this hobby. Especially when you're seeing flaky behavior.
People go hog wild replacing and repinning connectors, and it's often overkill and unnecessary, when all that's needed is removing a tiny bit of junk at the contact point that is interfering with two pieces of metal touching.
Also be aware that crimps can go bad as well. Any time two dissimilar metals touch, you can get oxidation between them. That includes between tin connector contacts and copper wires. But if there's a bad crimp, you should be able to narrow things down and find it, and just fix that one connection (often without even needing to replace the pin), and without needing to repin whole connectors.
Visual inspection under a BRIGHT light also often goes a long way here.