The work around to this problem is as follows:
1) Open the problem user (who created the report) properties, take a note of the options on the Settings page
2) Change Account Type to End User
3) Turn the 'Settings->Diagram->See Draft Maps' option on
4) Click OK to save changes
5) Open user's properties again
6) Change Account Type back to author/admin
7) Update the Settings page as required to restore initial state of the options
8) Click OK to save changes.
Note: clicking the Reset Settings button doesn't work without first changing Account Type.