Yes I know what you did. You must ONLY scratch the minuscule rectangular piece on the triangle. If the soldering touches the surounding triangular pcb you short.
Yeah i'm not too sure, the area I scratched is within the square. I can't help but feel like I am missing something else.
Here are photos of before and after.


If W11cE is reading this do you have any alternative locations for me to wire up if I can't get this spot to work? I noticed in your first images you've soldered to the bottom of the ribbon cable connector on the DS4 board, this might be a little beyond my skill set though judging by the size.
Can I use two USB leads one to DS4 triangle and one to Teensy, I know it is an ugly solution, but as a last resort anything is better than this not working.