Here are those better pictures I mentioned.
After further testing, I managed to track down the issue to the ac adapter. Didn't order directly from Dell, so probably was a knockoff.
By chance, do you know what specific version of the Dell brick you have? Is it LA330PM160?
No, it was DA330PM111. I bought it off Amazon instead of Dell directly though.
Huh. I picked up a LA330PM160 from eBay. Hopefully it's not a fake. No way to know until the system is built. I don't like the idea of getting one from Dell directly and it not being a LA330PM160.