12V *anywhere* on the Nano will destroy it! though the A... and D... leads are the most susceptible.
D7, with C130, is *supposed* to be a snubber for K1's back-emf on release of PTT, but is only that accidentally. Its top-layer track from the Anode goes to a 'via' down to the bottom-layer ground-plane, making it mainly a polarity-protector if you fit a fuse. I've excised the plane around the via, cleaning that off to create a pad which then takes a short jumper to K1.9. That gives it its intended purpose. On the diagram, delete the ground and place it below C130A (where is that on the board? is it really there?), disconnect the line to C130 and connect that to the *other* side of C130A (= K1.9).
