Making the Modification
The USB startup fix consists of adding a jumper between a resistor near the ribbon cable connector and a capacitor at the edge of the board. I'm assuming the capacitor is on the chip power supply coming from the 12V input and the resisotr is going to the reset pin of the USB chip. That would hold the USB chip in reset until the power supply comes up. Normally a mod like this would also include cutting a trace to break the original connection, but hopefully this will work!
These are 0402 parts so they had to be done under a microscope with my finest SMT tipped soldering iron and even then it was a challenge. I also had to carefully remove the conformal coating around the area.