Not working with headline widget

There seems to be an issue with the headline image. After several tries I found out that if I process data that was saved by the original SOPB, it works fine. However if I use this plugin the hadline widget inner html does not show up.
I suspect this is due to the fact that this plugin saves the widget data as JSON and the SOPB saves as serialized data?

But I cannot grasp what exactly is the issue here.

Any hint would be welcome.

Sascha