"Diagram is being re-generated" followed by a second error "System error"

When you try to display the diagram (image), two messages are displayed in turn. The first informative "Diagram is being regenerated" followed by the second error "System error"

 

If we look in the DevTool browser (F12) we can see the Console message that there are no rights to read the .png file (where the requested image is).

Furthermore, the Infoport log shows an entry about the inability to generate the image (typically reported by EA.Interop.dll / DCOM)

One of the causes may be a problem with access to the cache files, when something (failure, downtime, migration, etc.) causes the rights to the file caching the diagrams to be lost or locked by some process.

The files are available for reading (that's why most of them are displayed in Infoport), but as soon as they need to be regenerated (new diagram, change on diagram, etc.) it is not possible and the user gets an error in the browser. This is because when the Sparx DCOM is called, it failed to update the file on disk (in the cache).

The solution is to delete the directories that make up the \wwwroot\cache\* cache.