Recently i'm running Plone 5.1.2 from a Docker Image with Relstorage to use PostgreSQL as persistence layer. Everything is working fine so far. Now I wanted to modify my theme TTW (I just copied from the Barceloneta theme at the beginning).
But "Show inspectors" only creates gray frames and "Preview theme" opens a new blank page. Also on the Barceloneta theme.
I can confirm that the software installation is fine, when I start with a fresh database, the two issues do not exist. Probably at some point I misconfigured something that changed the database. I hope somebody faced the same issue and can point me to the right direction.