Panelizer displays broken with style: default after disabling / uninstalling this module

We ran into a big problem after trying this module. When we cleanly disabled and uninstalled the module, all our panelized nodes don't display any content anymore.
The fields and configuration are still present in the panelizer editing interface but the node display is empty.

I finally found out that the content is being displayed, if the region style: "default" is NOT used. But of course we'd still like to use it like before.

I've marked the priority as major because the module doesn't leave with a working website after unsinstall. I have no clue how to finally fix this and where to look for the problem!

Please help.