We are getting an error - after upgrading. It seems all charts now needs to have an explicit sharing settings to get the dashboard saved for non-super users..
Previously we could create charts and (no specific settings to charts) and place in dashboard and share it to a usergroup - this was enough for all in the usergroup to edit/save.
Yes, you spotted the change for version 2.40 and above. As mentioned in the v2.40 upgrade notes:
When updating a Dashboard, user is required to have METADATA_WRITE permission to the Dashboard itself and METADATA_READ permission to all referenced objects in all DashboardItems. Administrators can use cascade sharing in order to grant required sharing permissions when needed.
I hope that you are able to resolve this easily, please keep us updated!