So ideally when you migrate your website either from one domain to another OR to subdirectory, you have to change the Site URL & Home URL in WordPress Admin Dashboard also as WordPress stores the URLs in its Database, you can use some plugin(Better Search & Replace) which will search the old URL and replace it will new URL.
Hope this helps.
Thank you. I kind of gave up on this, and spent a couple of hours manually adding slash everywhere to make it work. For pages with many images used Dreamweaver to “replace all” with: /images