Hi,
I’m having the same issue, though in my case the unwanted characters are:
“>
It appears to me that there is an error (I think maybe a few errors) in line 1400 of the file wpr-mailchimp.php. I’ve tried editing this line and it seems to work, but obviously that’s just a temporary fix.
Original line 1400:
<form class="wpr-mailchimp-form" id="wpr-mailchimp-form-<?php echo esc_attr( $this->get_id() ); ?>" method="POST" data-api-key="<?php echo esc_attr(get_option('wpr_mailchimp_api_key')); ?>" data-list-id="<?php echo esc_attr($settings['maichimp_audience']); ?>"?>">
I think the last four characters – ?>”> – may be erroneous. Also note the incorrect spelling of “mailchimp”.