Description of my issue:
Got a 'One Click Update' email for a site, clicked on the link. Browser came up and two error messages appeared :
(In Red) JInstaller: :Install: Cannot find XML setup file
(In Blue) Invalid package type. The update can not proceed.
Then the standard Akeeba Backup "A new version is available" dialog is displayed at the bottom of the page.
When updating using the full 3.9.2 install package through the installed, it all goes fine.