@glyph this has been a life-saver. It does go through batteries faster than I'd like, but it's super fast and hasn't misread anything.

https://treedix.com/products/treedix-usb-cable-tester-usb-c-cable-tester-usb-tester-for-data-transmission-and-power-transmission-cable-testing-resistor-testing-type-c-emarker-for-usb-a-micro-b-micro-b-3-0-type-c-lighting-mini-b