using nRF Connect update FW success but actually fail..

  IC : nRF51822_xxAA
  SD: s130_2.0.1
  BL: SDK12.3 bootloader_secure with public_key
  MOBILE: iPhone 13 pro MAX with iOS 16.1.1

not always fail.  but often
How can I fix the bug?
the DFU app have same issue.

the attachment is process video, Pls help 

1. using nRF ToolBox(UART) check current version:1124
2. send command into DFU mode
3. using nRF Connect DFU and select file (
4. start upload file
5. APP SHOW "DFU upload was completed successfully!"
6. using nRF ToolBox(UART) check current version expect is 1125 but that still show 1124