Process of elimination.
We can try few things.
1- Live boot to the patched image, let's see if that works see the guides in OP, basically you remove the word flash from your command.
This will tell us if your root.img is good or not.
2- Switch slots and try on the inactive slot, but first factory flash that slot like you did this one and then try to flash the boot.img
If that works, then something about the boot partition on the current slot could be the issue.
We can try few things.
1- Live boot to the patched image, let's see if that works see the guides in OP, basically you remove the word flash from your command.
This will tell us if your root.img is good or not.
2- Switch slots and try on the inactive slot, but first factory flash that slot like you did this one and then try to flash the boot.img
If that works, then something about the boot partition on the current slot could be the issue.