i have similar issue as yours my board 820-01700 U8600 NAND had internal short on PP1V8
I replaced with one from iphone 11 tried DFU restore but gives err 6
I didn't tried to program the syscfg, as i only have JC for iphone 7 NANDs also there is 0 info about syscfg for Macs
and JC support didn't confirm if works for Macs just told me buy P11&try
before i put the used NAND tried to DFU restore&got err 4005
I replaced with one from iphone 11 tried DFU restore but gives err 6
I didn't tried to program the syscfg, as i only have JC for iphone 7 NANDs also there is 0 info about syscfg for Macs
and JC support didn't confirm if works for Macs just told me buy P11&try
before i put the used NAND tried to DFU restore&got err 4005