Fit Kit Station
This app is misleading. It's advertised as free app but it only does homepage optimization for free. To optimize rest of your website you would have to pay $9.99/month, which is mentioned nowhere on this page.
This app made absolutely zero difference to the speed of my website including zero difference loading the Homepage. I also tested it numerous times with Google Pagespeed, GTMetrix and Website Grader and none of them changed their rating. I was hoping for more speed but just wasted time installing it, testing it and uninstalling it.
We're so sorry to hear this.
We are running on more than 2,000 stores and currently don't have any issue. It might be because of other apps that change your theme and break links.
Would you mind sending us an email firstname.lastname@example.org so I can have a look for your specific store?