Question Error message: "The data in the EC or EC flash might have been corrupted. Shutting down in 15 seconds" ?

Light Speed

Mar 2, 2014
PC is about 10 years old with some gradual upgrades:

Mobo: m5a99x EVO R2.0
RAM: 4stick Aries 4GB (16GB ddr3)
GPU: GTX 1060
PSU: 650W

I have built a new PC since I last used this one with said problem, so it has been sitting in the corner for about 3 months, which it never has done before. All was working fine for a few days until suddenly the screens go black, fans still spinning, lights still on, case's power button does not function, solid red CPU light. Shutting down through PSU is the only option. Upon rebooting, all fans are spinning and all lights are on as normal until the American Megatrends screen displays "EC or EC flash might be corrupted. Shutting down in 15 seconds." Then it turns off completely.

I've tried reseating every component, re-plugging major cables. Temps on all components are normal. I thought updating the BIOS would be a solution but there is only one version (2501).

I've searched the internet and the only solution that shows results is resetting the CMOS by removing the battery for X amount of time and putting it back then booting up. I spam this method until it works again. Usually leaving the battery out overnight yields the highest chances for the machine to get onto the ASUS screen where I can boot up from BIOS and the computer acts normal again for about 2 days. The problem shows up again after long stints of actively using the computer (4-7hours), where the computer shuts down no matter what program is running (temps are normal). It's very confusing because nothing is consistent and it seems that no one online has experienced my situation of intermittent functionality.

Just today I figured replacing the battery would be a surefire fix but I was wrong. It's acting the same.