The problem occurs sometime when image get corrupted. I think only inode structure become incorrect.
If the reason is only this you can easily correct it via
After copying the image to sdcard you will need to correct the file checksum which somehow is failing and results in root partition mounted as read-only mode.
Use any linux machine and run below command
sudo fsck -y /dev/sdb2
where /dev/sdb2 is the linux partition