Exception Fill Line Colors not activated on report - when relative date used

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Can anyone explain why a report that use to show lines coloured as an exception are no longer coloured?

In design mode the lines are coloured when I run the report in Views - but if I save the report and run it from the Reports Explorer the lines are no longer coloured?

Other exception information on the report is visible - text in italics/bold

This seems to be a global issue not restricted to one report.

On further investigation it happens when the Exception is set to Relative Date e.g. less than -1 week exactly

It works if I use less than an exact date