Steps to reproduce:
PHP fatal error occurs:
PHP Fatal error: Call to undefined function bootstrap_form_process() in mydirectory/includes/form.inc on line 1850
I'm using latest version of Bootstrap Theme. It works fine with Bartik theme. Is this somehow related to https://www.drupal.org/node/2156371?
I had this issue, it was caused by the max_input_vars
PHP setting not being high enough.
Just open your php.ini
and set this with a high number (or higher than the one you already have set):
max_input_vars = XXXX