I am using the IFsh PEx component to write to flash on a MK24FN1M0VLL12. It has worked fine for storing configuration data and reprogramming parts of the flash, but it's not able to write to the last flash sector (Address 0xFF000 - 0xFFFFF). I have tried various routines: IFsh1_SetLongFlash and IFsh1_SetBlockFlash. They do not return any error, and no flash protection is enabled. I am able to manually modify the memory with GDB and J-flash, so I'm certain that it's not protected.
What could be causing this?