Buy X, Get X not working

We are having intermittent issues with the Buy X, Get X rule. when you click add to cart on any product, it does not add it. Also the cart in the upper right has a solid blue covering over it and doesn’t display the number. Something else that happens is if you click the all products link, it shows that site has a critical error. Her eis an error log that we grabbed that might can help assess the issue:

Error Details
=============
An error of type E_ERROR was caused in line 231 of the file /nas/content/live/cbdnew01/wp-content/plugins/woo-discount-rules-pro/App/Rules/BOGO.php. Error message: Uncaught Error: Cannot unset string offsets in /nas/content/live/cbdnew01/wp-content/plugins/woo-discount-rules-pro/App/Rules/BOGO.php:231
Stack trace:
#0 /nas/content/live/cbdnew01/wp-includes/class-wp-hook.php(303): WDRPro\App\Rules\BOGO::handleAutoAddFreeProducts(Object(WC_Cart))
#1 /nas/content/live/cbdnew01/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters(NULL, Array)
#2 /nas/content/live/cbdnew01/wp-includes/plugin.php(470): WP_Hook->do_action(Array)
#3 /nas/content/live/cbdnew01/wp-content/plugins/woocommerce/includes/class-wc-cart.php(1400): do_action('woocommerce_aft...', Object(WC_Cart))
#4 /nas/content/live/cbdnew01/wp-content/plugins/woocommerce-subscriptions/includes/class-wc-subscriptions-cart.php(327): WC_Cart->calculate_totals()
#5 /nas/content/live/cbdnew01/wp-includes/class-wp-hook.php(303): WC_Subscriptions_Cart::calculate_subscription_totals(53.47, Object(WC_Cart))
#6 /nas/content/live/cbdnew01/wp-includes/plugin.php(189): WP_Hook->apply_filters(53.47, Array)
#7 /nas/content/live

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