This situation occurs when you attempt to extract changes from multiple sources in different flexible condense groups. In a given extraction, you can only capture changes from a single condense instance or, in the case of flexible condense, from the same condense group. If you receive this message while you are attempting to move sources between condense groups, it is most likely because you did not correctly follow the necessary procedures. See the product documentation for information on the procedures necessary to successfully move sources between condense groups.