Date slicer not filtering custom visual

Hi,

I have a custom map visual built by a third-party that filters when you slice based on the underlying table data used in the map, but won't filter if you have a slicer displaying date from another table. There is a 1:M relationship between the date table and the fact table used in the custom visual. Using the built in map visual (bing) the date slicer influences the default map successfully.

When you use the date field from the fact table as the date slicer the custom visual filters fine.

What would be the common error resulting in the inability to slice using a field from another table when a relationship is established? 

J