Key chatter can arise due to different reasons and here I am going to list down all the causes of this problem and will tell you how to fix key chatter in mechanical keyboards permanently. If your keyboard is in warranty then you can issue an RMA request and get a replacement but it is a bit of time-consuming and it is also not guaranteed that the new keyboard will not face this chattering issue.
I personally have faced this key chatter problem with my Cherry MX Blue keyboard after only a few months of usage. Corsair, Ducky, etc.) that are having original Cherry MX mechanical switches. Outemu, Kailh, etc., but I have seen key chatter in branded mechanical keyboards too (i.e. The problem is more pronounced in mechanical keyboards with Cherry MX Clones or Chinese mechanical switches i.e. Key chattering can arise in single or multiple keys in a mechanical keyboard and it generally arises when the keyboard gets older, but it can also occur in brand new keyboards too.