I recovered a bricked grey Jag today by using a black Jag, RS-232 Adapter and the the BDC-COMM application.
It was recovered over the CAN port.
I didn’t think it would work at first, but I had the Black Jag configured for Board #7, chained up the bricked grey Jag, and used the recover option in BDC-COMM using the grey Jag firmware.
It breathed life back into our grey Jag.
Afterwards, I updated the firmware on the black Jag, making sure it was the only device on the chain, and explicitly using the black Jag firmware.