Flash programming error (Flash Key violation) when executing code from RAM

I have found a problem when programming internal Flash from code located in RAM and it looks like it has been reported before in this thread: 

e2e.ti.com/.../312665

In my case, I have an MSP430F5338 and I'm using IAR workbench.  The code is compiled in large code/data model.  When the Flash Write function is located to execute in RAM, I occasionally get builds that will often fail during a Flash Write function call, other times it works fine.   When the function is executing from Flash, then it is always reliable (obviously the code is located in a different Flash segment than what is being written).

I captured the failure (when Flash Write code function is in RAM) and what is happening is that during the wait loop for the busy bit (see code segment below), I occasionally get a "Flash Key violation" reset.   The Flash Key violation suggests that one of the FCTL registers has been written a value that does not have 0xA5 in the upper byte.  You can see that interrupts (and also watchdog) are turned off.  Is this a known problem with the silicon?  Are there limitations that I have not obeyed?

Thanks,

Michael

The flash write function looks like this :

// inputs:
// nBytes: # of bytes to write
// address: Flash target address (already erased)
// buf_ptr: uint8_t pointer to source data in RAM

{

  Flash_reg* flashReg_ptr = (Flash_reg *)0x0140;
  uint16_t count = 0;
  uint16_t gieStatus = __get_SR_register() & GIE; // save interrupt state

  __disable_interrupt();

  //! Ensure status is not busy
  while (flashReg_ptr->fctl3 & 0x01)
  {
  ;//! Do nothing, wait up to clear the busy bit
  }

  //! clear lock bit and write password 0xA5
  flashReg_ptr->fctl3 = 0xA500;
  //! write password and select byte write
  flashReg_ptr->fctl1 = 0xA540;
  
  while (count < nBytes )
  {
    *((uint8_t *)address) = *(buf_ptr + count);
    address++;
    count++;
  
    //! Wait to clear busy flag
    while (flashReg_ptr->fctl3 & 0x01)
    {
        ;//! Do nothing, wait up to clear the busy bit
    }
  }

  //! clear WRT bit
  flashReg_ptr->fctl1 = 0xA500;
  //! //Set LOCK bit
  flashReg_ptr->fctl3 = 0xA510;

  __bis_SR_register(gieStatus); // Restore interrupts
}