Merge Fails When Trying to Merge Salesforce-Synced Leads in Marketo

[#1]

Issue

Issue Description
You try to merge two records in Marketo and a System Error appears ‘Failed to merge leads [Lead ID]'

Solution

Issue Resolution
One of the reasons why the merge fails is the leads are part of a different account in SFDC. Even though it looks like they belong to the same account, you need to verify their account ID in SalesForce to see if they match.

Another possible reason is due to lack of permissions on SFDC.