Just in case someone else comes looking for a solution, I tried swapping out all references to PATH_INFO to ORIG_PATH_INFO but I get the same ‘URL not recognized’ message when I try to select an issue for publication, plus some more such messages in other places (e.g. the main Submissions page)
Interestingly, the endpoint being generated was exactly the same:
https://osotl.org/index.php?journal=osotl&endpoint=/osotl/api/v1/submissions/13/publications/13
For reference, here are the locations where I changed the PATH_INFO variable (on the server - this screenshot shows the local copy of OJS I used to locate instances of PATH_INFO):
I am now reverting back to using PATH_INFO so other parts of the site aren’t broken.