Your grub seems quite oldass and possibly faulty.
Now if you want to quickly workaround this issue then do the following.
Open Fx and go to System(Root) > /data/ghome
Enable Hidden Files from top right menu icon of Fx (If you haven't already)
You should find a file called .gearlockrc in there (/data/ghome)
Open it as a text file and put this line of code at the bottom of it.
/gearlock/gerroot is the place where your C: drive got mounted (You installed PrimeOS on C: drive, right ?)
android is the folder name inside your C: drive in which your PrimeOS is installed. (So basically that's why its /gearlock/gearroot/android/)
Let me know if this helped ;)
Edit: By the way, I had already implemented a way to auto detect your kernel image when its missing, but seems like that didn't work, just fixed it out today. You can just update to GearLock 6.8 and you won't need to do what I just said above.