Error at Data Flow Task [Pivot [28]]: Output column "TransMonth" (49) cannot be mapped to PivotKey input column.

TITLE: Package Validation Error
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Package Validation Error

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ADDITIONAL INFORMATION:

Error at Data Flow Task [Pivot [28]]: Output column "TransMonth" (49) cannot be mapped to PivotKey input column.

Error at Data Flow Task [SSIS.Pipeline]: "component "Pivot" (28)" failed validation and returned validation status "VS_ISBROKEN".

Error at Data Flow Task [SSIS.Pipeline]: One or more component failed validation.

Error at Data Flow Task: There were errors during task validation.

 (Microsoft.DataTransformationServices.VsIntegration)

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BUTTONS:

OK
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Resolution: 

1. TransMonth column was added in the list of output columns. By removing this column from the output columns the issue was fixed.
Note: There can be many reasons for this error.