When updating a Dynamicweb solution, you need to keep an eye on all the important notes provided by Dynamicweb Software. However, I encountered this undocumented feature today when I was updating a Dynamicweb-solution from version 8.2.1 to 8.4.10. All of a sudden all items disappeared.
I investigated the release notes, and made sure to verify all item settings in management settings – to no avail. The solution was to check the “Include paragraph items” on each paragraph containing the itempublisher-module (sigh!).
Just like this: