Using Bootstrap theme and anonymous user, ajax form submit results in "call to undefined function bootstrap_form_process" Context

We have a subtheme based on the Bootstrap theme and we're rendering a form inside of a modal. The submit button uses an ajax callback to handle form submission.

Problem

When logged in as an admin in Chrome, the form submits perfectly.

When logged out (accessing the site as an anonymous user) in Chrome, submitting the form results in a 500 Server error.

The server logs are reporting "Call to undefined function bootstrap_form_process()".

Research

It seems that this might be related (https://www.drupal.org/node/2156371) but I'm not sure what to do to fix it.

I have a hard time following issue discussions on drupal.org. I have a decent amount of Drupal knowledge, but still struggle to figure out what they are saying.

Things I've Tried

Some people in the thread linked above got around the issue by setting max_input_vars to 2000, so I gave that a shot. It didn't help.

I thought maybe I needed to increase it even more, so I set it to 5000, but still no change. I then switched it back to the default 1000.

I also tried adding "drupal_static_reset('element_info');" to my theme's template.php file, but it didn't seem to do anything.
This is similar to https://www.drupal.org/node/2369635, i.e. you need to include /path/to/bootstrap/includes/process.inc in your codebase.  The easiest way IMHO is in a hook_init() somewhere.