Translating custom fields!

I stumbled across the same problem.
If I add a new content element to a page with this plugin:
https://wordpress.org/plugins/multiple-content-blocks
a new editor field shows up for the second content element.
But this editor only has the tabs text/visual. It is missing all my language tabs.

I am not fluent enough in php to find a patch myself, but I assume there is a simple solution.

Thanks in advance!