Thanks.
I actually think I know what the FF is now. It seems that a new board with no faults in its memory shows 1FF, 2FF, 3FF, etc. up to 10FF. When a fault happens it takes the place of 1FF and moves all other faults up 1.
Since changing the board it is now saving faults and allowing me to find what the problem is. The previous board was only showing FF's in the fault log. Something must have went wrong with the board for it to stop registering faults and also erase previous faults.
