This forum post, saying that it turned out to be a faulty engine control unit seemed to be the most similar to my case, although it's an older model. (mechanics.stackexchange.com)
That means lithium - ion battery packs, electric motors, hardware such as wiring, and even software such as engine control modules. (digitaltrends.com)
These increases were the result of engine control tuning that together with other technologies combine to create excellent power characteristics, exceptional fuel efficiency and very low exhaust emissions. (greencarcongress.com)