Could you please let us know which field you’re experiencing the issue with? Is it one of the default WooCommerce fields (like billing_phone, billing_email, etc.) or a custom field?
If it’s a default WooCommerce field, then we would like to let you know that we are using the WooCommerce default email, phone validation in our plugin. You can check the same by temporarily deactivating our plugin Checkout Field Editor for WooCommerce.
Further, if this is not the exact issue, then could you please provide a bit more detail on the problem? This will help us better understand the problem and assist you more effectively.
Thank you!