Possible problems?

I’ve got a 2014 Prius with 152k miles. I’ve owned the car for about 5 years and have had no issues thus far.

2 weeks ago, CHECK HYBRID SYSTEM popped up on the screen. Car still drove fine, got it home, parked it for about a week. Tried driving it again, wouldn’t go over 25 mph. Checked the codes and did some research and seemed like the inverter went bad. Replaced it with a used inverter and car drove perfect for about 5 miles, CHECK HYBRID SYSTEM popped up again.. but this time seemed like the 12v battery died. Got a new battery from Walmart, put it in and all the codes went away and car runs perfect again.
Drove it 205 miles, been running good all week.

This morning the CHECK HYBRID SYSTEM sign came back while I was letting it warm up. I turned it off and took my other car to work. When I came back in the afternoon and started the car, the sign is gone and the car runs good again.

It has one code showing up P0A08.

The new 12v battery is at 12.28 volts when car is off, but jumps up to 14.45 when I start the car. I put the battery on charge and I’ll drive it around again and see if anything changes.
Inverter pump seems to be working, a little bit of movement in the tank when car is on ready.

The only thing I’ve noticed that a little different is the inverter pump noise when I turn off the car is sometimes keeps going for a solid few minutes. Sometimes it shuts off after about 10-15 seconds after shutting off the car, the other time it stayed on for a while. Always turns off immediately if I lock the car.

Can anyone point me in what else to check?

 

Yes, turns out it was the headlights making that noise. I put in aftermarket headlights and I guess never noticed how noisy they were

 

Turns out the noise was from the aftermarket headlights I have installed, I unplugged it and the noise stopped.

I don’t have all the codes from the original problem. But almost all of them had to do with the inverter.

 

EDIT

After I posted this, I figured out the noise the car was making was the aftermarket headlights I have installed.
Also, I couldn’t get the 12v battery to get to a full charge. So I returned it and bought another new from Toyota.
Installed the new battery and I changed the positive side terminal plus the fuse with it.
Car drove perfect for about a week, 1100 miles. Randomly right after startup today, the same P0A08 code came on. I am using a Innova 5610 code reader, so nothing fancy.

With the car off, the battery is showing 12.85 volts. So I can rule out the 12v battery being an issue this time.

After turning the car off twice and letting it sit for a couple minutes.. the code went away.

Could it be the used inverter I bought, is not working properly? Or something else?