I had a similar issue a month ago, went the new PS route and like you, problem continued. I took out vid card and memory then gave them a quick sanding with 2000 grit paper then an alcohol wipe and reinserted. Then removed every SATA connector on MB and drive and gave all a light spray with INOX and restarted, problem gone. As a LOL I did not properly restrain a PS cable and it wound up eventually blocking the fan on my AIO, the CPU then went to 98C and promptly BSOD'd. I think you've found your problem by moving it out of the case and running it going breadboard, now find a good cleaner/lubricant and do a through contact cleansing while it's out of the case and easy to do. I like the INOX because it's not greasy like WD-40. I think all of us are guilty of forgetting just how many connections are involved with a modern machine and the consequences of just one of them not functioning properly, best of luck and welcome to AT, while not as big as it used to be, still balls-deep in nerdpower!