JetPack related posts plugin stopped displaying related post results few months back when I shifted the servers to DigitalOcean VPS and started using nginx as web server instead of Apache. Together with JetPack Sharing plugin not working and related posts not displaying, I started searching logs to find what is wrong? but I didn't find any errors or warning in the logs and my website on nginx was working perfectly without any errors.
On Internet there are many users complaining about Feedbacks of Contact form Plugin in JetPack Thrashing their database. Even I got almost over 11 Thousand Spams in Feedbacks, Deleting them one by one is a hassle and WordPress throws an Error when I try selecting around 100 feedbacks and deleting them, so I had to find another way to delete Feedbacks all together and it's useless data.