The dimension '[Current Date]' was not found in the cube when the string, [Current Date], was parsed

I have a large cube with multiple Order, Invoices, Quote and goal information that I process everyday.   On the average, I get the following error about once a week.   Once the error occurs, I resubmit the processing and the cube completes successfully but it puts me hours behind schedule. 

MdxScript(Sales Customer Performance) (4330, 5) The dimension '[Current Date]' was not found in the cube when the string, [Current Date], was parsed.

and Current date is defined as

CREATE SET CURRENTCUBE.[Current Date]
AS
    TAIL( FILTER( [Transaction Date].[Transaction Date Hierarchy].[US Working Date].Members, NOT ISEMPTY( ( [Transaction Date].[US Working Date].CurrentMember, Measures.[Gross Sales $] ) ) ), 1 ).Item(0);   

Werner