My Fairphone 3+ bricked in the same manner as above, I was able to unbrick the device by going back to FP3-6.A.039.7 using this guide ( Fairphone 3 unlocking without oem unlocking ) and flashing the device with the full FP3-6.A.039.7 fastboot package to unbrick the device without data loss, I do hold off a week to attempt to avoid such issues but the dice rolled against me this time
It has been unlocked in the past and flashed with magisk boot images but I did flash it with the latest (at the time) full fastboot image before relocking and formatting the device