DemandTools V Release can now tackle Salesforce limitations related to merging records when 'Contacts to Multiple Accounts' is enabled.
Salesforce Limitations
When merging contacts with different account relationships using the native Salesforce merge function, the merge will fail with the error, "Can't merge contacts." To execute the merge, redundant relationships will have to be manually removed.
Similarly, when attempting to merge accounts that are indirectly related to the same contact, the merge will fail with a similar error and users will again have to manually remove the redundant relationship before the merge will execute.
Resolution
Using the Dedupe module in DemandTools, accounts and contacts with redundant relationships can easily be merged without throwing errors and without having to manually remove any redundant relationships. DemandTools will automatically remove the redundant relationships so the records can be merged.
Merging Contacts with Multiple Account Relationships
When merging contacts with multiple account relationships in DemandTools, all accounts relationships will be moved to the master record. The Account that is listed as the direct account on the master record will remain and all other accounts will be indirectly related.
Merging Accounts with Shared Contacts
When merging Accounts that have indirect relationships with a shared contact, the redundant relationship will be removed, and the accounts will be merged. The contacts are moved to the master record and all direct and indirect relationships will remain intact.