Report Card anomaly

I have been amending EMC's report card report; when a client is not in production it is moved into a group beginning with zz and afterwards it is moved out so I have written a report that creates an "inclusion list" which then joins with the standard data source for this report.  All is well and good, but I found that if a client had been in a zz group earlier in the week but is no longer in it, it is excluded from the report. 

The simple answer seems to be to create the inclusion list from the current time rather than the period of the report.  I tested it and it generates the information correctly.  When I join them the report card has no lines.  After much head-scratching and trial and error I decided to look at the table behind the report card to see if anything is generated there, and it is creating what looks to be valid data with the same columns as the report card that does work, but for some reason this slightly amended data does not do anything (also it is now returning the data for the clients that are no longer in zz groups!)

Has anyone met anything like this before and figured out a resolution for it?