Editor fails to open after upgrading to WordPress 5.6

After upgrading to WordPress 5.6 I am experiencing a very annoying problem that makes it impossible to update my sites :(

When editing a page I can see all the rows and widgets. However, when I try to edit the text in a SiteOrigin Editor widget the editor fails to open – instead I see only a timestamp with current date and time in the upper left corner – the rest of the page is empty. No error message is displayed – just an empty page except for the timestamp.

If I add a new SiteOrigin Editor widget I can edit the text, save the changes and view the new page content – however, next time I try to edit the page all SiteOrigin Editor widgets fail to open the editor – even the widget I just added. I just displays this empty page with the timestamp.

I tried changing to a default theme and temporarily deactivated all plugins to see if any non-SiteOrigin plugin was causing the problem. After deactivating the Wordfence Security plugin from Wordfence (!) SiteOrigin worked like before upgrading to WP5.6 – the editor opened and I was able to edit my text.

However, I need to keep the Wordfence Security plugin activated at all time to keep my sites safe so uninstalling this plugin is not the solution.

Any help on how I can still keep using the Wordfence Security AND use the SiteOrigin editor again would be greatly appreciated!

/Lars