There are no triggers on the table.
The table has records periodically imported into it, every 5 minutes. Records were created as follows:
integrationQueueID, Created
7002 - 7018, 11:20am
7019 -7023, 11:25am
7024 - 7029, 11:30am
7030 - 7032, 11:35am
On the 11:40 attempt the sequence somehow had been reset to 7002 and the duplicate primary key error occurred.
The import had worked for days and then suddenly the sequence reset to something that had been generated 4 iteration earlier.