All URLs changed path after upgrading to 3.6?

I’m not sure exactly what has changed here. All links are directing to "site.test/admin/site.test/blog/{slug}", when clicking on the link from the entry page. Before they would be "site.test/blog/{slug}". All links across the entire site are doing this. Is there a new variable or setting I need to change?

I have the sites ‘Base URL’ set to an .env variable, $PRIMARY_SITE_URL which I then have set as ‘site.test’