Hi as far as I know there has never been a case of inverter failure , well thinking about it maybe one but I leave myself to be corrected, but in other words it is extremely rare.
There has been a recall that happened about two years ago for the RX 400 owners to go in and have The faulty module changed free of charge so you'll probably find yours is either had it done or can have it done at the local Lexus dealer. I'd ask who you have you bought it from or whoever you are buying from , if it has had it done
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