Reported for: WooCommerce Multilingual 3.6.11
Resolved in: WooCommerce Multilingual 3.7
When using WooCommerce Multilingual with WPML, WooCommerce and WooCommerce Bookings, deleting a reservation does not trigger deleting the corresponding translations.
This was fixed in WooCommerce Multilingual 3.7-beta3 available form the WPML.org downloads page.
Also, this patch needs to be applied to WooCommerce Bookings 1.7.13.
The fix will be available in the next WooCommerce Bookings version by default.