propel.request.id Is Being Added To The Beginning Of Interaction Title

We've installed SMA-SM and connected it to HPSM. Now, whenever an Interaction is created in directly in HPSM (not through service portal) the value in propel.request.id is being added to the beginning of the Interaction title. This only seems to happen to users who have RESTful API and SOAP API capabilities. I've used the find string utility to search on all relevant tables for propel.request.id and cannot see what is causing this behaviour.

What is controlling it, and how can it be stopped?