After upgrading a Plone site from 5.2.1 to 5.2.2, all plone-* related JS files are no longer being loaded (5.2.1 on the left, 5.2.2 on the right)...so functionality like folder_contents is no longer working:
The resource registry tells me something about a build error (I do not see any error messages on the console).
There is also a (pointless) hint to enable the debug mode for the resources registry inside the configuration registry....which key in the configuration registry is this exactly?