Sorry, got to doing some research, and went off into unknown territory. Was hoping others would chime in.
My initial impression was, wow, that's a really low voltage. But then I found that 100v is standard in Japan. The fact that the car charges fine at 40 amps suggests the car is fine, but then why wouldn't it draw power at the lower voltage. I'm presuming that the car can auto-voltage down to your standard 100 volts. I don't recall anyone mentioning a special version or such for Japan. More likely, the 100v power was problematic somehow. I have found that the logs on my car don't reflect changes in current applied during a charge session, so what you are seeing is one snapshot (beginning or end, I don't remember) during the brief charge session, and not the whole history. If there was a problem during the session with the wall power (e.g. voltage sag), I don't know that you'd see it. Seems silly not to log it, though, since that would be an important event to remember. I haven't had a chance to try charging my car with a long extension cord to see what would happen in real life. Didn't get farther than that.
Seeing as how it recorded only 1-10 amps out of a configured 15 is most likely due to voltage sag, and that the problem was not with the car. Assuming all seems fine now, I'd go with that. You might check the contacts on the end of the 100v charging cable to see if there's any evidence of burned contacts (they'd look scarred or blueish/blackened). If it was the charging cable, that's an easy thing to replace.
Perhaps one way to look at it, even if there is an item for repair, the price seems low enough to still be a reasonable deal. But, that's coming from one who spent about 2x what you're looking at (and was happy doing so). I almost didn't pursue getting my car, over concerns about large investment, and the all the unknowns. The seller offered me a 7-day/250 mile return policy, and my family talked me into going for it. Glad they did.
