I also faced this error.
But i found that solution that, CF7 already reserved some variable tag for their form control.
such as [type name] [type email] etc.
Thus why, when you assign your variable value with like that you will see error message & may not work properly.
so please avoid using the generic variable tag in your form control.
if you want to get First Name, Last Name & Email you should assign like that
[text* fname]
[text* lname]
[email* visitoremail]
