You're performing a double update on the record being integrated. It's surprising how often this happens, you just don't see it until Unifi fires twice. Check the history of the record being integrated, are there two updates at the same time? This usually happens when a before rule inserts a record in another table, and that table then updates the initial record, creating a double update i.e. new incident saved with a CI, before rule on incident inserts a new Task CI record for the added CI, after rule on Task CI adds a work note to the incident causing a double update.