It sounds like you probably have the city or other dimension on the columns or rows shelf. Make sure that only Latitude and Longitude are on the rows/columns shelf and place any other fields on the marks card.
Hope this helps!
I have the same issue but my long/lat are correct.
> I have geo info [district,county, state] in FileA
> blending 'customer' info [customer, city, state] in FileB
These 2 files successfully linked by 'state'.
When I move 'customer' to Marks, I got one dot per 'district' instead of multiple.
In a separate file, I have 'customer' successfully mapped using CUSTOMER and CITY as ATTR but this doesn't seem to help my blending effort. Now, I'm brain-head from troubleshooting whether I have a CITY/DISTRICT conflict.