Electric Issue

that can be a tricky diagnosis. could be corrosion anywhere in the car, a loose connection, chewed wiring and etc.
start with the battery negative to ground connection, then a free load test at autozone

 

I've had this same problem intermittently for years and soon as I resolve to finally diagnose it goes away and I don't bother... What's basically going on is the shut down sequence when you turn the car off goes wrong and it's likely the circuitry that sits on top of the positive side of the 12v because whenever I'd wiggle that stuff around it'd start working normal again.

Next time you power off your car watch your speedometer and if the gear shifting part of the screen turns off at the end of the shut down/ last in the sequence things are normal. But if the gear shifting part of screen turns off at the same time as everything else the 12v is now disconnected entirely and will usually reconnect in a second, sometimes forgetting what happened and powering up the car into ready mode with warning lights, even without the FOB. Then you turn it off and turn it on again and it works normally again. At least usually.

Eventually if it one day is no longer a random problem and needs to be fixed I plan to take everything apart back there where the 12v is and clean and inspect and reassemble.

 

Have someone inspect it for cleanliness and tightness.
How many miles on her, it might be time to start car shopping

 

The ground wire is very short it goes right from the negative terminal of the battery right below the tail light to the chassis or metal or body If you undo the 10 mm screw that holds the ground wire from the battery to the chassis you want to clean up any corrosion off of that piece you're holding in your hand and on the metal that the 10 mm bolt goes through the battery terminal end into the chassis You want to make that nice and clean It should have a good ground space usually silver metal is good for that then after you put it together and tighten it up you could spray some CRC red battery terminal protector on that connection you just cleaned and made that will help that stay nice for a long time then the battery terminals on the battery itself should be lead silver colored nothing growing on them no white material any of that If so they make things to clean the terminals of your battery It's like a brush you stick on the terminal and screw righty tighty lefty loosey doesn't matter has little metal fibers in the brush that will clean the terminal to bright silver and then it hasn't external type brush that you stick into the battery cable that you took off and run that brush around in that and that brings that back to silver copper looking color and then again you make the connection you could spray a little battery terminal protection stuff on it very lightly very. Put that back together any water getting in to the battery tray area the 12 volt area You need to look at this carefully I took a 1/4 in drill bit . And added some strategically placed holes so that any pass-through water that comes through the gasket or wherever they think it's coming from hits that floor under my battery and goes right out of those little quarter inch holes that I put water standing in the battery tray and freezing in the winter will take out a 12 volt immediately with the bottom of the battery sitting in a half inch to an inch of water even with it not being extremely cold can take the battery out very quickly so after the battery's been frozen or sitting in an inch of water in it's well where it sits well more than likely take out the battery meaning make it bad It's like taking the battery out and sitting it on concrete that can suck the juice right out of a battery pretty quick. I'm imagining you're probably having 12 volt troubles giving the water and the funny business going on in the back where the battery sits The tail light is usually not an issue water comes down the tail light seals even if it's leaking It's vertical The water's trying to run down to the ground not down into the car body and then still down so if you need to take your tail light out you can look and see this where your water's coming in is generally the channels where the struts for the rear hatch lay down when you close the hatch tree funk leaves dirt and crap pile up in this area that people clean once every year or so and that helps water to stay in that trough where the shocks lay down when you close the hatch All that buildup of the tree funk the dirt and the nonsense holds the water doesn't allow it to flow down the channel hit the rear bumper go on to the ground It helps make a damn it builds up halfway down the channel under the hatch goes under or over the gasket runs down behind the plastic drips into the plug for the fan and then works its way over there into the battery tray area the 12 volt I have watched this in two of my vehicles before I cleaned and got that area to flow properly again then it doesn't happen keep from parking it under trees and the stuff never gets in there to make it happen.

 

Not sure where in FL you are but a visit to Tampa Hybrids might be in order. The biggest issue with these cars is getting someone "good" to work on them. Dealers can be very expensive but have the best knowledge and tools. I do not understand why there aren't gen2 specialists all over the country, they seem to last forever if maintained properly.
Anyway back to you, the car is controlled by a computer who knows maybe more than one. If it loses power for a fraction of a second it causes problems. Water in the battery area is a well known issue, which helps connections get nasty and possibly intermittent. Having done battery replacement and cleaning of connections down there more than once I can say it is not hard but can be challenging. Wires are very thin and corrosion makes them prone to breaking. Space is rather tight for a beginner and shorting out the battery terminals will make sparks that are scary to a beginner. Your car is young in mileage and could last a very long time, just need the right person to look after it. Sounds like the current person isn't.

 

You'd be more glad if it didn't happen anymore because I already diagnosed it and told you there was an easy way to fix it... Haven't found the time to look at it more closely yet. I wonder if @Elektroingenieur or @ChapmanF has any thoughts about the circuitry that attaches to the top of the 12v and the specific component/loose connection that could be causing this?

 

In a Gen 2? The little fusible link block that sits on the battery + post is nothing more than that. It has places for two wires to the front of the car to plug in, and a fuse for each one. One of them is a fat wire with a fat fuse (the power for the car), and the other is a skinny wire with a skinny fuse (just running to a voltmeter inside the inverter housing up front so the charging voltage is known).

So with nothing being there but copper-on-copper wiring connections, if something flakes in and out when you wiggle it, not much to look for besides flaky connections.