When duplicating a “Changes Only” data source map, data appears to still be looking at the old map id resulting in unexpected results.
When making a duplicate, the query needs to be edited to reflect the new map name.
1. After making the duplicate open up the new map
2. Press the Data Source button, and click on the Modify button in the lower right corner.
3. In the Query Builder window, change the source query to point at the new map ID.
4. There is a section there that says [MapId]=’XXX’ where XXX is the Map ID of the original map. You need to change XXX to the new Map ID
5. Click OK on the Query Builder window, click OK on the Data Source window and click Save on the Map Setup window. The map should run successfully now.