Error last update v.1.0.3.8

Since the last update, a critical error has appeared with an old form. Can anyone help me?

Detalles del error

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Se ha producido un error del tipo E_ERROR en la línea 408 del archivo /homepages/17/d343158015/htdocs/afib/wp-content/plugins/send-pdf-for-contact-form-7/classes/generate.php. Mensaje de error: Uncaught TypeError: Cannot access offset of type string on string in /homepages/17/d343158015/htdocs/afib/wp-content/plugins/send-pdf-for-contact-form-7/classes/generate.php:408

Stack trace:

#0 /homepages/17/d343158015/htdocs/afib/wp-content/plugins/send-pdf-for-contact-form-7/views/send-pdf-admin.php(357): WPCF7PDF_generate::wpcf7pdf_create_csv()

#1 /homepages/17/d343158015/htdocs/afib/wp-content/plugins/send-pdf-for-contact-form-7/classes/send-pdf.php(332): include('/homepages/17/d...')

#2 /homepages/17/d343158015/htdocs/afib/wp-includes/class-wp-hook.php(341): cf7_sendpdf->wpcf7pdf_dashboard_html_page()

#3 /homepages/17/d343158015/htdocs/afib/wp-includes/class-wp-hook.php(365): WP_Hook->apply_filters()

#4 /homepages/17/d343158015/htdocs/afib/wp-includes/plugin.php(522): WP_Hook->do_action()

#5 /homepages/17/d343158015/htdocs/afib/wp-admin/admin.php(264): do_action()

#6 {main}

  thrown