SYMPTOM:
Two grids contain a common attribute and the attribute in both grids is used as selector targeting the same graph. The selections in two grids are not synchronized in Strategy Web 9.3.1.
STEPS TO REPRODUCE:
Follow the steps below to reproduce the issue with Strategy Tutorial project:
1. Create a report with Region and Profit.
2. Create a document against the above report.
3. Add two grids with the Region attribute and a graph in the document.

4. Use the two girds as selectors targeting the graph.
5. Select "Central" in Grid A.
6. Select "South" in Grid B.
7. Note that the selection in Grid A doesn't change to "South".

CAUSE:
This is a known issue in Strategy Web 9.3.1.
ACTION:
This issue has been fixed in 9.5.1. Please upgrade to take advantage of the fix.