Changes to be committed:

[frederickOtus]

  modified:   index.php
  modified:   lib.php
  modified:   mod_form.php
  modified:   view.php

From: https://secure.php.net/manual/en/function.include.php

"Files are included based on the file path given or, if none is given, the include_path specified. If the file isn't found in the include_path, include will finally check in the calling script's own directory and the current working directory before failing. "

In some cases, the require_once('locallib.php') call was finding other instances of locallib.php in the moodle code and ending, rather than loading this plugins code.

Notably, I experienced this with attempts to recover grade histories for students getting re-enrolled in courses with an instance of this module in their grade history