Loop Error When Trying to Update an SR Field via Workflow

I've encountered a loop error while attempting to update a Service Request (SR) field using a workflow. Here's the scenario:

I've set up a workflow where, in one step, I populate data from the SR to a Local Action Item. The configuration is as follows:
SR | Last Present Data -> Last Present Data | Overwrite if not Completed | Action Item Activated.

This setup works perfectly fine. However, I now need my staff to be able to update this field, and for those changes to populate back to the SR. 

I attempted to implement the following configuration, but it resulted in a loop error:
SR | Last Present Data <- Last Present Data | Overwrite | Action Item Completed.

How can I successfully update this field without encountering a loop error?