In the main menu (click the “hamburger” icon in the top left of the Roon window), choose “Instellingen” and then “Over” in the list. That will list all your devices that are running Roon, and start the upgrade process for any that need it.
If all devices are up to date, then restart your Roon Core (reboot the Windows 10 PC that is running the Roon Core) - this “Metadata verbeteren” message has been known to pop up in error - a reboot of the Core should cure it.
Hello @Hendrik_Kroon and thanks for your report! Could you please reboot your core and see if the Metadata Improver message goes away? We have seen this issue in the past and a reboot has resolved it for most people. Thanks!