Edited
This is the well known S3 sleep bug, lucky you have it on your BIOS if you are trying to flash mod BIOS and locked out by FPRR settings. This is first thing to check in those situations, go to sleep, resume and see if you can then flash
If you are only wanting to solve the issue, update to latest BIOS, if it’s not solved then only the manufacture can correct it (ie let them know, see if they will send you fixed BIOS)