Reported for: WPML Multilingual CMS 4.5.9
Resolved in: 4.5.10
Overview of the issue
If you are using Classic Widgets plugin, you will notice that when you add a widget and you use the Display on language feature to display it only in one language, it will be visible in all languages.
We have currently released WPML 4.5.10 which should solve this issue.
Please, don't hesitate to make a full backup of your site first and then update your WPML plugin as explained on this tutorial.