Compatibility with Mandrill

Was just testing it on a site using Mandrill with wp-mandrill plugin. Was unable to send test emails after customizing templates. I switched to the wp-mandrill settings and tried sending test email from there and got this error:

Warning: Illegal string offset 'html' in /home/username/example.com/wp-content/plugins/email-templates/includes/class-mailtpl-mailer.php on line 85

Warning: Illegal string offset 'tags' in /home/username/example.com/wp-content/plugins/wpmandrill/wpmandrill.php on line 1868

Warning: Illegal string offset 'user' in /home/username/example.com/wp-content/plugins/wpmandrill/wpmandrill.php on line 1868

Warning: Illegal string offset 'tags' in /home/username/example.com/wp-content/plugins/wpmandrill/wpmandrill.php on line 1868

Fatal error: Cannot use string offset as an array in /home/username/example.com/wp-content/plugins/wpmandrill/wpmandrill.php on line 1868

Not sure if its an issue with wpmandrill or with email templates.

https://ww.wp.xz.cn/plugins/email-templates/