500 Internal Error when leaving the item after commenting process

Hi Guys,

I'm using Komento within several Applications (ZOO and JDownloads) and I'm struggling with a 500 Internal Server Error in both applications but also by testing it in a Joomla article.

The commenting process works fine and the comment is published.
The error occurs when I leave the item.
Within the ZOO application a browser refresh before leaving prevents the error - but not in Joomla or jDownloads.

Any idea?

Thanks in advance for your assistance
Ralf