vendor/magento/module-sales/view/frontend/email/order_new.html:
<!--@vars {
"var formattedBillingAddress|raw":"Billing Address",
"var order.getEmailCustomerNote()":"Email Order Note",
"var order.increment_id":"Order Id",
"layout handle=\"sales_email_order_items\" order=$order area=\"frontend\"":"Order Items Grid",
"var payment_html|raw":"Payment Details",
"var formattedShippingAddress|raw":"Shipping Address",
"var order.getShippingDescription()":"Shipping Description"
"var shipping_msg":"Shipping message"
} @-->
There is a trailing comma missing after "Shipping Description"
This issue also exists in the order_new_guest.html
more info