I’m having the very same problem but with automatic registration processes (quick and full) from the FOG’s grub menu.
I’d say the problem is actually the ‘/var/lock’ folder as it makes no sense to me that ‘touch’ cannot create a file, so I’m guessing it’s the actual path what doesn’t exist. But where? … the path exists in the FOG server so … not sure where should this path be created … 
I’d appreciate some help from FOG devs 