Issue

Adding an item to an K2 integrated SharePoint list or a document to a SharePoint library, and updating the metadata when prompted by SharePoint, causes the associated Workflow to start twice.

Cause

Adding an item to the list or library fires the add item event and adding metadata when SharePoint prompts you, fires the update event. If you set the Workflow to start when you add an item and when you update an item as shown in the following image, the associated Workflow will start twice.
Image

Resolution

Configure the workflow for the list or library to start only when one or the other event occurs.