If the browser becomes unresponsive or very sluggish when you open a dashboard, the solution from this article may help you.
Why does the browser hang when opening/editing a dashboard?
There may be multiple accumulations of entries in the Dashboard.xml. If this is the case, the browser becomes sluggish when opening the dashboard designer and sometimes stops responding.
Open the path C:\Program Files\C4B\XPhone Connect Server\AppLink\DashboardConfig\Current on the XPhone Connect Server.
Then search for the Dashboard.xml and save a copy of the original. Then open the file and check it for repeating lines.
Remove repetitive entries:
Make sure that no syntax errors are formed.
Save the file and then check the behavior again.