I am getting a rather strange popup after changing a page type. See attached image.

The problem with this popup is that I can't hide it, it reappears after page reload. Not sure if that is related, but I had some incorrectly set server permissions, so the first time I tried to change the page type the change couldn't be written to the /config directory which resulted in an error message.

If I click on compare versions it just shows me the preview of the current page version and an empty preview (I deleted all other page versions).

Any ideas how to fix this?

Thanks.