Cannot update file if any configuration settings are arrays

[blackdrago]

Using Laravel 5.4 with php 5.6

Whenever I try to change existing keys -- ANY existing config keys -- I receive this error: Unable to rewrite key "email_recipients" in config, rewrite failed.

Email recipients is an array of email addresses. Sometimes it's empty. But it's always an array.

I am using the repository model as a variable $config, and whenever I try to user $config->set($key, $value) then $config->save(), I get this error. Even if "email_recipients" is not being modified at all.

However, if I go into the config file and change the array of values for email_recipients to false (or any value), the $config->save() works without issue.