12V Switched Has Power When Car is Off

I've had a helluva time trying to get my headunit - Kenwood DPX-5200BT - setup in my car - 2013 Skoda Fabia. I'll save you all the backstory, but here's the current issue:

I have a VAG Quadlock to ISO adaptor and the included ISO to Kenwood 16-pin adaptor. I've checked they are wired correctly according to a few sources on Google/the user manual. When I connect everything up, the unit turns on, and will function perfectly normally, except for the fact that it always has power. It won't turn off with the key and I can even turn it on when the car is completely off.

I've tried switching around the red (switched) and yellow (power) wires as the manual suggested, but all that has revealed is that both have constant power. The head unit is functioning perfectly as far as I can tell, so it must be a car issue.

Any ideas as to how I can further diagnose the issue, what might be the issue, and how I can solve it?

TL;DR - both switched and live power from the harness provide constant power regardless of ignition state.