Lock-up after attempting to upload secure bootloader

While testing the "Secure Bootloader" and "Secure Firmware" instructions I found that Mission Planner locked up after pushing the "Bootloader Update" button. <img width="1533" height="1131" alt="Image" src="https://github.com/user-attachments/assets/bf86c1fb-f086-4a46-9af6-86034b7fa477" /> <img width="1297" height="256" alt="Image" src="https://github.com/user-attachments/assets/8e9c6a67-c494-4be0-b6ac-a429d4a92ed6" />