OK, so I replaced all 4 diodes (I used 2x 5818G and 2x5820G), see pic. A little ugly, I think. I took voltages and they are way off - B6 is 225VDC, A2 is >550VDC (and there was a strange noise when my multimeter probe touched that lead), and when I hooked onto that resistor hanging off the soft start board I got 90VDC.
Any thoughts? I'm happy to try any suggestions, but this feels like I should send it in, maybe?