Sorry for ignoring your post. But I have little to go on. What type of PSU are you using? Is it connected to the UPS? Formatting your system might help but I rather just do a reinstall and keep all your stuff but again. I don’t think it is the main board is the problem I think there might be a driver problem or just a corrupted DLL that forces to see your PSU to ignore the command line thus you get the safe to switch of your system error before your system such itself off. DELL actually has a setting that forces the computer to switch of manually. So take a look at your power setting under your BIOS. Sometimes it just need a restore session to fix the DLL’s But right now I am grasping at straws...