Problem:
WooCommerce account endpoints were giving 404 in secondary language Solution:
The user is not using WCML as it has issues with his plugin Smart Coupons.
The WooCommerce Endpoints slugs were translated. Remove translation from String Translation under "WP Endpoints" domain.
Problem:
User was unable to translate checkout fields Solution:
User was using the "Checkout Fields Editor" plugin, and was already settings labels for the fields in primary language(not english).
The plugin stores the fields as theme options. You either translate through admin strings or using this xml.