According to Google’s updated content guidelines for the FAQ schema, no longer can you markup the same question and answer with FAQ schema if that question and answer is in multiple pages on your site. The company said to just mark it up on one of those FAQ pages, and no more than that.
The updated guidelines added this line “If you have FAQ content that is repetitive on your site (meaning, the same question and answer appear on multiple pages on your site), mark up only one instance of that FAQ for your entire site.” @suzukik spotted this.
FAQ schema was designed to be added to FAQ pages that provide frequently asked questions and answers on specific subjects. By adding this type of data, it will help Google show questions and answers directly on Google Search and the Assistant.