Yes, it appears that it doesn’t work with a plugin called Front-End Users. It disabled access on wp-admin which was interfering with the update to the DB. I tried installing the front end plugin that you developed, though when attempting to activate it. I get the following error.

Plugin could not be activated because it triggered a fatal error.

Fatal error: Call to undefined method WeDevs_Settings_API::getInstance() in /wp-content/plugins/wp-user-frontend/admin/settings.php on line 13

I should also add that the user is also unable to add or remove anything from the To-Do list or messages.