KUMA has some limitations that are not critical for the operation of the application:
After upgrading KUMA 3.4 to version 4.0, some widgets on the dashboard are displayed with an error. To fix the error, please manually refresh the data on the dashboard or wait for it to be refreshed automatically.
The widget form can be opened below the Dashboards settings form when you follow links from the Used in widgets column if you have opened the settings of any widget before opening the Dashboards settings form.