Error code after form submission

I am recieving the following error code after form submission, with deactivated stylesheet and javascripts and text in the hidden field.

Notice: Array to string conversion in url() (column 2084 von /*****/includes/common.inc).
Warning: Illegal offset type in isset or empty in drupal_lookup_path() (Zeile 125 von /*****/includes/path.inc).
Notice: Array to string conversion in drupal_lookup_path() (column 131 von /*****/includes/path.inc).
The requested page "/Array" could not be found.

The email is (as expected) not being submitted, but the code is printed.
With activated stylesheets and javascript the email is sent on submission and no error code is showing. (works also as expected)
I am using the module together with the webforms (7.x-3.13) module.
Any ideas why this happens?
Best regards,