"cks" files do not belong to iGO software.
They were probably transferred from a computer

Edit: I remember that I see them in Avic only. Not sure that they belong there. Probably some internal software format, like checksum. All cks files are 12B.
Maybe have something to do with the wrong entry in sys:
[interface]
save_checksum=0
Anyway, it is always advisable to delete those tails as well.