Unable to restrict results with workschedule filters when it is blank or non primary

Summary:

Issue: There are multiple subject areas combined together to generate results which is embedded in dashboard. A new change has been requested to include employee's workschedule along with start date. After adding this, there are multiple records that are being returned for an employee with inactive/nonprimary workschedules as well. There is no luck despite trying various formula/analysis filter/dashboard prompts. I have come across similar thread but could not figure out how the result column was built. Link here

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