Moved and renamed a module, but drupal_retrieve_form() is still looking for the old one

I had a sub-module that needed to be moved out and made into it’s own standalone module (and renamed it). I’ve done this, but when I try to configure the new stand-alone module I get a message:

Notice: Undefined index: old_module_name_edit_form in drupal_retrieve_form() (line 807 of /var/docroot/web/docroot/includes/

Obviously, I’ve tried cleaning the cache and registry.

Would anyone know what I can do to fix this?

Line 807 looks like:

$form_definition = $forms[$form_id];

if it matters.

Drupal version: