hook_node_insert PDOException exception issue
You cannot call node_save($node) during hook_node_insert($node).

According to the documentation, that hook is invoked during the middle of the database transaction, so the node isn't committed to the database yet. So when you invoke node_save, the old node you're attempting to update doesn't exist yet, and it will attempt to create a new node (with the same ID). Thus, the collision.