Yeah, but the dell thing isn't a hardware induced reaction to poor quality power, it's an arbitrarily imposed restriction based on the lack of the third sensor pin. Is this a "thin" client mini-PC that's powered off of a power brick, and are you using a non-OEM brick?
When you google M900 Tiny you get this:
Learn more about the space-saving ThinkCentre M900 Tiny, the most powerful tiny desktop per cubic inch, and its built-in productivity, reliability, manageability, and security features for enterprises.
You seem to be working in the right direction. Strange if it was fine and then started to go though. So many different possible combinations of hardware, so many possible points of failure. About the only good thing about Apple is their iron grip on their hardware. Still overpriced hardware, but they control it.