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BIOS resets due to power loss. "Common problem for Aorus boards"... This has not been my experience. I have 4 Aorus boards, and none of them dump bios settings. I only use intel based paltforms, but there haven't been any posts from AMD users reporting this issue I can recall. (Random reset due to power loss)
Lots of causes for something like this. Bad flash, over clocking, A mis-match of hadware components.
~Bad or corrupt flash (examples):
BIOS image being used to flash is incomplete or corrupt
BIOS flashing process is interrupted
Flashing in windows using @BIOS, instead of QFLASH
Running beta release BIOS versions
~Over-clocking (examples):
Specifying or using settings outside of hardware capability (CPU, Memory) voltages, timing or CLK speeds
System resets (after power loss) might occur here as a form of system "recovery"
~Using mismatch or non QVL Components (examples):
Unmatched memory sets or using memory which is not listed on the QVL for your board
Substandard components, low quality or underpowered power supply
B450-M
F50 hasn't been what I would consider reliable. All CPU's are currently supported as of F40 or earlier. Since flashing itself is inherently risky, doing so just to have the latest available isn't best practice. What we don't know about your build are the components you used or if you are "pushing them". Since you have flashed and used other BIOS versions with the same results, I would look at your hardware and component choices. Second at the BIOS settings you are using. What happen if you run "defaults" shut down and unplug the system. Does the BIOS still reset?
Resets from power loss is not normal. You should not have to live with this or accept it as common behavior.