Hi Werner,
Thanks for reaching out to us! I’d be happy to help you 🙂
The bug you’re refering to has been fix earlier this year. I just tried on my local installation and it works properly (WPML translates all instances of an event in a recurring event series).
Can you confirm you click on “Edit All” before creating a multilingual version of a recurring event? If so, and if WPML only create one recurring event, then it might be due to a conflict in your website, in which case you would have to test for conflicts.
I hope this helps,
Cheers,
Jeremy