WHMCS bridge error when submitting a ticket

The WHMCS bridge v1.3 is working fine, however the only error we are getting at this time is when a ticket is submitted: see attached screenshot.

The path is correct in the error message.

Error message:

"Catchable fatal error: Object of class WP_Post could not be converted to string in /home/idshost1/public_html/wp-content/plugins/whmcs-wordpress-integration/whmcs-integration.php on line 587"

I have WHMCS in this location:
and my website in this location:

To duplicate:
- goto http://idshosting.co.za
- click Client area on the top menu
- click Submit Ticket
- click Sales
- enter ticket info
- submit

Hope to get this fixed soonest as I need to upgrade to v6 of WHMCS this weekend as well, currently on: 5.3.7

Please advise soonest.

PS: I have deactivated all the plugins and the error is the same, currently running BETheme.