Resolved
Reported for: WooCommerce Multilingual & Multicurrency 3.6.4
Resolved in: WooCommerce Multilingual 3.6.5
Overview of the issue
When editing a product translation using the standard product editor, existing translations of custom attributes are being deleted.
Workaround
Use the WooCommerce Multilingual products editor to edit products translations or download WooCommerce Multilingual 3.6.5-beta1 from the WPML.org downloads page.