Kona intermittently powers down hard when turned off - possible 12v battery issue?

[EVOwnerFromDownThere]

On my 2020 Kona Ultimate, I'm having an intermittent issue where the car seems to "crash" or power down "hard" when I park it and press the ignition switch to turn the car off.

Normally, when I park the car and go to turn it off, I'll get the chime, the radio will continue playing, etc. Intermittently, I'll push the button and everything will immediately go black - even the dome lights. A few seconds later, I'll hear a noise that sounds like it's coming from the HUD unit, a soft clunking for a few seconds. If I have my foot on the brake, it acts like any brake assist was immediately removed and forcefully pushes towards the default position.

When I power the car back on, it turns on just fine, but the infotainment stays on the Hyundai logo boot screen for 20-30 seconds minimum, and the HUD rises up (I never use the HUD, so it's in the lowered position).

I haven't been able to replicate this issue on-demand, but it's been happening more often over the last couple of months, I'd say at least once a week lately. Has anyone seen this behavior before? I don't have any other symptoms of a bad 12V battery.

 

[KiwiME]

I don't think this has been reported anywhere before. But I would suggest having a closer look at the 12V battery because I would expect that it's relied upon to supports the car's systems momentarily during a graceful shutdown. Buy yourself a battery monitor from Supercheap and you can monitor this easily with your smartphone. It's not practical to use a simple voltmeter to accomplish this.

https://www.supercheapauto.com.au/p/century-century-bluetooth-battery-monitor---bm12v/601801.html#q=battery+monitor&lang=en_AU