The BIOS update 0077 mentions USB/boot related fixes, you could test you computer with that version.
Note before updating your BIOS in your Intel® motherboard, jumping from an old version to a newer version with some updates in between could affect your system, please check the recommended procedure below:
1. Look for the next BIOS version available (not the latest, the next from the current version in your system), and update to that version.
2. Continue with the next version once the update is done, do this until you get the version 0077.
Some useful information that you can take into consideration
The desired BIOS version would be 0077, please test your system with that version after following the BIOS update procedure.
Also, check that "boot from USB first" is not selected in your BIOS; additionally, check the boot order of your drives, note this external drive is not in the first options to boot.
I look forward to your outcome with this.