Solved
It's working as expected.
The widgets like Dropdown list & Grid are just data receiver, when you select 1 row of data inside, you're pointing to the source service, and the selected row of data will be presented in all widgets that's linked to the output of this service. We always use this function to co-related between different widgets. i.e Select 1 row of data from infotable result in Grid, and present the details in related charts.
What's your expectation on putting 2 drop down widget to same service as source?
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