Portable version problem

When I overwrite the existing portable folder (I am using as ‘JabRef_port’) from the compressed file, overwrite all folders&files of course, JabRef does not start. Neither seen in taskmanager.
When I extract the zip and rename the JabRef folder to my custom name, deleting the old folder in my favorite folder, then moving the new version there, Jabref works normally.
Win 10, v1909.