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You make perfect sense, many things in these miners are hard to be explained because they don't make sense, but I have personally had issues that did seem to be PSU related and ended up being hash boards related, I initially thought of it the way you do now, it's pretty simple, the control board controls both the PSU and the hash boards, so any power related issue must be PSU or control board, but well, shit happens.
I encoured a similar power issue on a T17, I don't remember the exact error in the kernel log, but it was "power xx error", I tried a working PSU and a working control board and that didn't fix it, I played with the hash boards and the miner worked, it turned out that one of the hash boards was causing the issue, the miner worked perfectly with 2 boards.
What I did next was installing that "bad" hashboard on another T17, and guess what? it worked without an issue, I installed the hash board which I took out from the second T17 on the first T17 and it worked as well! do I have a technical or scientific explation for this? No, and i am sure even Bitmain themselves don't.