Checkout Error After Update to 1.8.4

We are getting an uncaught error at checkout with version 1.8.4

2021-02-02T18:49:57+00:00 CRITICAL Uncaught ArgumentCountError: Too few arguments to function Atum\MetaBoxes\FileAttachment::attach_files_to_wc_emails(), 3 passed in /var/www/html/wp-includes/class-wp-hook.php on line 287 and exactly 4 expected in /var/www/html/wp-content/plugins/atum-stock-manager-for-woocommerce/classes/MetaBoxes/FileAttachment.php:138
Stack trace:
#0 /var/www/html/wp-includes/class-wp-hook.php(287): Atum\MetaBoxes\FileAttachment->attach_files_to_wc_emails()
#1 /var/www/html/wp-includes/plugin.php(212): WP_Hook->apply_filters()
#2 /var/www/html/wp-content/plugins/woo-product-bundle/includes/class-woosb.php(2831): apply_filters()
#3 /var/www/html/wp-includes/class-wp-hook.php(287): WPCleverWoosb->woosb_low_stock()
#4 /var/www/html/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters()
#5 /var/www/html/wp-includes/plugin.php(551): WP_Hook->do_action()
#6 /var/www/html/wp-content/plugins/woocommerce/includes/class-wc-emails.php(170): do_action_ref_array()
#7 /var/www/html/wp-includes/class-wp-hook.php(287): WC_Emails::sen in /var/www/html/wp-content/plugins/atum-stock-manager-for-woocommerce/classes/MetaBoxes/FileAttachment.php on line 138

Rolling back to version 1.8.3 fixes the problem.

I think it might coincide with an item being low in stock.

Woocommerce Version 4.9.2
Running PHP version: 7.4.9
WordPress 5.6

If you need more information please let me know.