For example, if I try to flash a bootloader this is the situation
C:\Program Files (x86)\WugFresh Development\data>fastboot flash bootloader bootloader-grouper-4.23.img
sending 'bootloader' (2100 KB)...
OKAY [ 0.568s]
FAILED (remote: (InvalidState))
finished. total time: 0.710s
and on the nexus 7 appears "signature mismatch".
and the cases of other partitions of a stock firmware are similar