If it were me, I would take the code for low battery voltage to heart with these ECU's.
Sometimes it's the simplest things that make things happen in weird ways!

Your car seems to be running fine except for the brown outs and shut downs!
GENERAL MAINTENANCE may be missing.

How old is the battery?
Have you had it load tested to see if it's working up to its rated capacity? Old batteries can and will wane in different ways.
Do you have a in the dash voltmeter? It can shows some habits within electric system that can forecast doom down the road, if you watch and become savvy to it!

When was the last time that the main cables were removed and cleaned?
When was the last time the fuse panel was given the same like treatment?

Best you get the power supply tuned up! When you are getting a steady supply of current/voltages coming in, that's when it you can point fingers at the components that might control the actual shut down.

Intermittent issues are the most troublesome to track down without a having a base line of where they cannot start from. Good troubleshooting requires a check list that you have nice solid "X's on it!

Reliability comes from reliable maintenance. Doesn't cost much to be tidy.

Phil