the webassist/email/mail_php.php file had become corrupted on your server.
I updated that file with a fresh one, but these 2 files are also corrupted.
webassist/email/waue_contact_us_1.php
webassist/email/waue_sample-request_1.php
delete them from your site, remove the UE server behaviors from the pages, and reapply them to regenerate those files.