Plugin activation breaks email validation in other plugins

Hi there, when I activate this plugin I begin to get errors in other plugins (ie WP-HR) when trying to create a new user with an email address. The error I get is “Please enter a valid email address.” regardless of the email address being perfectly valid. This goes away when I deactivate this plugin. In this particular case, the email address is rejected in the wp-admin backend, so there’s no link to a frontend example I can give at the moment.

Thanks!