Error during checkout and Empty values in email

Hello,

I had the free version installed but recently it started producing an “Internal Server Error” during checkout. I installed the premium version and the error persists.
When most other plugins are disabled, the checkout goes through, but the email arrives with empty values. The error log has this entry:
[14-Jun-2023 13:03:30 UTC] PHP Warning: Trying to access array offset on value of type null in /home/…/wp-content/plugins/woocommerce-email-template-customizer/includes/email-render.php on line 1474

Do you know what could be causing this?

Thank you