So sorry to hear that you had to deal with this hassle, and I hope that it is a quick fix. As others have noted, the 12v can often be the culprit. We had 2011 and 2012 Leafs, and replaced their 12v before they got old, never had any issues. We also had a 2019 Leaf, and that 12v went bad early on. The message it gave was "Service EV System No Power", and there hadn't been any hint of trouble leading up to it. We hadn't noticed any increase in the frequency of self-charging of the 12v, but now that I think about it, maybe that could be a problem... I took delivery of my Ariya about a month ago, and after bringing it home and parking in the garage it was doing the self-charging bit for like three hours straight. The Leafs never self-charged for that long. I haven't noticed that it has done it for that long again, but it does like to charge its 12v. I just home-charged today up to 80%, and right after unplugging, it started a 12v self-charge.