Hi Weiyan. Can you return the instrument and ask for a replacement? You might also return it, get a refund, and buy another one from a different supplier. If it is still under warranty, maybe you can have Yamaha service it for free.
I bought a Hohner Piano 36 about 10 or 12 years ago. The cost was $180. It arrived with less than perfect tuning. So I contacted the store I bought it from, and they either tuned it or they had me send it to Hohner for retuning at no charge. I can’t quite remember the details, but it was re-tuned for free. Lowboy