I have tested this on both a Linux and Windows box and experience the same behavior. Both machines are running Pentaho-Server-CE 126.96.36.199-12. The Linux box is running OpenJDK 1.8.0_131 and the Windows machine Oracle JRE 1.8.0_151.
Steps to Reproduce
1. Create new CDE Dashboard
2. Go to the Components Panel
3. Add a new Simple Parameter give a name and property value
4. Save the dashboard as a Widget
5. Go to Settings and Check the Widget Parameter created in Step 3
6. Click Ok
The web page will appear to hang, and has reported a 404 timeout on syncronizeDashboard. I haven't noticed any other errors in the Tomcat logs. If the workflow is repeated the servers CPU and memory usage will continue to climb.
Any help in identifying a workflow issue, bug, or workaround would be greatly appreciated.