Error when setting up {client} in ticket auto reply

[pecmo]

1. When setting up the ticket autoreply and selecting {client} in subject or body it won't send the email.
2. Setup {client} in subject or body (it shows as an available tag) emails won't send and logs will start growing exponentially with the follwing error:
3. general.ERROR: Uncaught Exception Error: "Object of class stdClass could not be converted to string" at /home/*****/public_html/portal/vendors/blesta/h2o/h2o/datatype.php line 23
4. Include the URL the error occurred on, relative to the installation path, ie "/admin/login": NA.
5. When oppening the ticket it shows a blank page, email won't send.
6. Blesta 5.5.0, 5.5.1 and 5.5.2, PHP 7.4 & MariaDB 10.3.

This happens only when using this tag in particular, not with {contact.first_name} or any service/billing tags.