New car / ‘Lemon law’ for defect?

I purchased a new car from a Honda dealer (hybrid Stepwagon) just under a year ago. At the beginning of this month, on a road trip, the 12V batter died twice. Both times, the rear gate was left open for an extended period of time (around 6 hours) but the engine and all dome lights were completely off, as were the majority of cars around us (beach parking lot). Everyone we were with (about 6 separate cars) all agreed it was very unusual for a battery to die just from leaving the gate open. We made it back home and Honda took the car in the next day. They’ve had it for early two weeks now trying to find the issue but were unable to. They proactively decided to exchange parts related to the rear gate as well as the 12V batter and the 12V battery itself. However, since they haven’t clearly identified the issue. I’m concerned that this might not be a permanent solution. Also, unrelated to the battery issue, but the loaner car we received (also hybrid Stepwagon of about the same age, I believe), when stopped at a red light with my foot on the break, suddenly switched into reverse for about one second (made the reverse sound and the navigation monitor switched to the back camera) before switching back to Drive. This also concerned me and, as this is our first hybrid car, leaves me feeling not so confident/comfortable.

I’m wondering if anyone has similar experiences (maybe even with different issues) with newly purchased cars in Japan. Does anyone have any knowledge or advice regarding consumer protection laws? Also, am I just being paranoid about the potential of future issues?

Thanks for any insight anyone can share!

Edit: i should add, on this particular trip, the battery actually started fine after the first 5-6hours of having the gate open. The batter died after moving to a different parking lot and leaving the gate open for an additional hour.

Also, after getting it jump started, we drove to the nearest gas station and had the battery tested. They said it was holding a normal charge and shouldn’t be an issue.

Also, on a previous outing, we had sudden issues wuth the automatic slide doors not opening.

All of this combined is what gives me concern.