RosCMS caught an exception, can't ranslate latest pages modifed by frik85

Procedure:

"all entries", filter: "about", change on the 2nd parameter "and language is" -> english (tried other ways too).

The first entries (all frik85's) are:

about
about_history
contmenu_about
about_press_articles
about_press
about_press_kit

clicking on any of them will make RosCMS produce this error:

RosCMS caught an exception to prevent data loss.
If you see this message several times, please make sure you use an up to date
browser client. If the issue still occurs tell the website admin the following information:
Name: TypeError; Number:undefined; Message:this.getDoc() has no properties, Description: undefined

I see the page's code but I can't use the richtext editor.