Here’s an example to more easily demonstrate what I mean from above.
2 Sites:
1st site: example.com
2nd site: example.com/second-site
If I visit example.com first, I am served example.com. If I then visit example.com/second-site I am also served the correct site. However when I go back to example.com after visiting example.com/second-site I now get served the example.com/second-site.