STM32G474 SPI DFU mode not working

I'm using STM32H753 eval board as master and STM32G474RE Nucleo board as slave over SPI1 communication. I've created a DFU for LED blink on Nucleo board which works fine if I download it through USB(connected PA11, PA12, 5V and GND) usinf DeFuseDemo tool. have set BOOT pin and all option bytes to enter into bootloader(system memory). If I connect it in SPI mode, I get ACK for all commands there is no single error in communication, all 5704 bytes from DFU file are written successfully. here is my code,

	/* boot loader process starts */
	blInit(&hspi1);
 
	blGetCommand(spiRxBuffer);
 
	version = blGetVersionCommand();
 
	chipID = blGetIDCommand();
 
	/* Check GetVersion is equal to GetCommand version */
	if (version != spiRxBuffer[0])
	{
	 /* TODO : exception handler */
	}
 
	/* Erase, write & verify loop #########################################*/
	/* @note The Flash has to be erased before it can be written to */
 
	/* (0x44) Erase Sector 0 (2 KBytes) */
	blEraseMemoryCommand(0x0002, 0x00);	
	/* (0x31) Write firmware image */
	if(blFWUpdateFlags.bUpdateImage)
	{
		copyImagefromFlash(devType, fname, buffer);
		blFWUpdateFlags.bUpdateImage = 0;
	}
uint8_t copyImagefromFlash(uint8_t devType, char *filename, uint8_t* buffer)
{
	uint32_t len, temp;
 
	if(lfs_file_open(&lfs, &slaveImageFile, filename, LFS_O_CREAT | LFS_O_RDWR | LFS_O_APPEND) != 0)
	{
		MPC_TRACE("\nSlaveFW.txt cannot be open\n");
		return FILE_ERROR;
	}
	else
	{
		MPC_TRACE("\nSlaveFW.txt is open\n");
 
		lfs_file_read(&lfs, &slaveImageFile, &dfuFilePrefix, ELEMENT_HEADER);
		stDword(&slvElement.dwElementAddress, &dfuFilePrefix[3]);
		stDword(&slvElement.dwElementSize, &dfuFilePrefix[7]);
 
		//if(devType < STM32G07_DEV)
		{
			len = slvElement.dwElementSize;//(slaveImageFile.ctz.size - (OPTBYTE_STM32G47x + 8));
		}
		//else
		//{
		//	len = (slaveImageFile.ctz.size - (OPTBYTE_STM32G07x + 8));
		//}
 
		len = (len / SLAVE_PAGEMEMORY_SIZE);
 
		for (int i = 0; i < len; i++)
		{
			lfs_file_read(&lfs, &slaveImageFile, buffer, SLAVE_PAGEMEMORY_SIZE);
 
			blWriteMemoryCommand(slvElement.dwElementAddress, SLAVE_PAGEMEMORY_SIZE, buffer);
			slvElement.dwElementAddress += (SLAVE_PAGEMEMORY_SIZE);
		}
 
		len = slvElement.dwElementSize;
		len = (len % SLAVE_PAGEMEMORY_SIZE);
 
		lfs_file_read(&lfs, &slaveImageFile, buffer, len);
		temp = (slaveImageFile.ctz.size - slvElement.dwElementSize);
		if(devType < STM32G07_DEV)
		{
			if((temp) > (OPTBYTE_STM32G47x + 8))
			{
				temp = 1;
			}
		}
		else
		{
			if((temp) > (OPTBYTE_STM32G07x + 8))
			{
				temp = 1;
			}
		}
		if(temp == 1)
		{
			lfs_file_read(&lfs, &slaveImageFile, &dfuFilePrefix, ELEMENT_HEADER);
			//stDword(&slvElement.dwElementAddress, &dfuFilePrefix[3]);
			stDword(&slvElement.dwElementSize, &dfuFilePrefix[7]);
			temp = (SLAVE_PAGEMEMORY_SIZE - len);
			buffer = (buffer + len);
			lfs_file_read(&lfs, &slaveImageFile, buffer, temp);
			buffer = (buffer - len);
			blWriteMemoryCommand(slvElement.dwElementAddress, SLAVE_PAGEMEMORY_SIZE, buffer);
			slvElement.dwElementAddress += (SLAVE_PAGEMEMORY_SIZE);
			len = slvElement.dwElementSize;
 
			len = (len / SLAVE_PAGEMEMORY_SIZE);
 
			for (int i = 0; i < len; i++)
			{
				lfs_file_read(&lfs, &slaveImageFile, buffer, SLAVE_PAGEMEMORY_SIZE);
 
				blWriteMemoryCommand(slvElement.dwElementAddress, SLAVE_PAGEMEMORY_SIZE, buffer);
				slvElement.dwElementAddress += (SLAVE_PAGEMEMORY_SIZE);
			}
			buffer = (buffer + len);
 
			for (int i = len; i < SLAVE_PAGEMEMORY_SIZE; i++)
			{
				*buffer++ = 0xFF;
			}
 
			blWriteMemoryCommand(slvElement.dwElementAddress, SLAVE_PAGEMEMORY_SIZE, buffer);
 
		}
		else
		{
			buffer = (buffer + len);
 
			for (int i = len; i < SLAVE_PAGEMEMORY_SIZE; i++)
			{
				*buffer++ = 0xFF;
			}
 
			blWriteMemoryCommand(slvElement.dwElementAddress, SLAVE_PAGEMEMORY_SIZE, buffer);
		}
		lfs_file_close(&lfs, &slaveImageFile);
		return FILE_OK;
	}
 
}

Did anyone use DFU - SPI mode to update slave FW, would you please let me know where could be the issue.

thanks,