Greetings,
This is a known issue. If you leave DADman in Sum mode (not Switched) you should be able to successfully toggle between Sum and Intercancel for the Monitor sources from the S6 surface Soft Keys or Monitoring Page.
http://avid.force.com/pkb/articles/e...vid-S6-Support
DADMan: Source selection Sum and Intercancel mode setting conflicts with S6 Monitoring mode setting (GWSW-9640)
The S6 Monitoring local options page lets you configure Source selection for Sum or Intercancel mode, and this setting can conflict with the same settings available in DADMan preferences.
Workaround: Do either of the following:
In the S6 Monitoring local options, set Source selection to Sum mode and then only use DADMan preferences to switch modes.
Configure DADMan preferences to Sum and only use S6 to switch modes.
Jeff