Hi,
Sure! Thank you for the details, it helps us a lot! I noticed, that not only the filter labels, but the values also change for each product translation, for example: https://i.imgur.com/8pNZ8SR.png
However, the plugin only registers strings for the labels to translate. To resolve that, I made a tiny change to one of the plugin core files, to register the custom field values for translation as well. If you go to the WPML string translations board, you should be seeing them under the [CF Filter Value] strings now.
Please try translating those as well, so the filter values change accordingly. Let me know if that resolves the issue, and I will make this change permanent for the upcoming release.