Jump to bootloader not working on STM32H7 rev "V". Bug in bootloader?

[PMath.4]

I'm launching the bootloader from within code using previously posted examples. This works fine on "Y" and DFU enumerates as expected. On rev "V" this doesn't work - no enumeration. Has the entry point changed on rev "V" or is this a bug in the bootloader which I believe is a different version in rev "V" and which other threads indicate has issues?

Is there a way of getting the bootloader entry address? SYSCFG.UR3 gives the top 16bits but where is the rest defined?

  uint32_t i=0;
  void (*SysMemBootJump)(void);
 
  /* Set the address of the entry point to bootloader */
     volatile uint32_t BootAddr = 0x1FF09800;
 
  /* Disable all interrupts */
     __disable_irq();
 
  /* Disable Systick timer */
     SysTick->CTRL = 0;
 
  /* Set the clock to the default state */
     HAL_RCC_DeInit();
 
  /* Clear Interrupt Enable Register & Interrupt Pending Register */
     for (i=0;i<5;i++)
     {
	  NVIC->ICER[i]=0xFFFFFFFF;
	  NVIC->ICPR[i]=0xFFFFFFFF;
     }
 
  /* Re-enable all interrupts */
     __enable_irq();
 
  /* Set up the jump to booloader address + 4 */
     SysMemBootJump = (void (*)(void)) (*((uint32_t *) ((BootAddr + 4))));
 
  /* Set the main stack pointer to the bootloader stack */
     __set_MSP(*(uint32_t *)BootAddr);
 
  /* Call the function to jump to bootloader location */
     SysMemBootJump();
 
  /* Jump is done successfully */
     while (1)
     {
      /* Code should never reach this loop */
     }