I saw a lot of logs (P3X_FW_LOG_AB.txt or P3S_FW_LOG_AB.txt) where downgrading using debug file was madeim trying to just go from 1.9 to 1.8 on a new bird i got, i'm seeing this alot:
[00000668][01 00] Firmware upgrade finished failed (step = 3, err = 0xffffffff).
this camera has a broken off gimbal .. but figured the mainboard should still be able to flash the bird. Thoughts? its not creating the main fw log in the root directory.
and they all have one common thing:
downgrading is done in two steps
in first, firmware of [01 00] is updated
then the FW bin file is reread again and FW of the rest of modules is updated
so I believe that [01 00] is doing all the upgrading and downgrading - at first it updates itself and then (with new FW) it updates the rest of the modules
conclusion for you is, that if you have some problem with [01 00], I am afraid you won't be able to downgrade (and maybe even to upgrade)