This thread is resolved. Here is a description of the problem and solution.
Already translated products lose the translation when updating the original product.
This issue was caused by the Enhanced Category Pages plugin. This plugin has not been updated for two years and only tested up to WordPress version 4.5.13. It is recommended not to use it.
This is the technical support forum for WPML - the multilingual WordPress plugin.
Everyone can read, but only WPML clients can post here. WPML team is replying on the forum 6 days per week, 22 hours per day.
This topic is split from https://wpml.org/forums/topic/several-faulty-product-urls-outputted-to-crawling-and-sitemap/