If the number of fraudulent ratings is under 100, I highly doubt it's bots. In that case it's someone you most likely know, who has narcissistic personality traits. The person aims to upset you. Don't let them win by getting you upset.
If you think you know who is most likely behind this and especially if you have memories of the person targeting toxic behavior towards you before, I suggest removing the person from your life, as narcissists are very destructive and manipulative. They can be super charming and really good actors when it comes to playing unethical mind games with others for self excitement.