PF: AGS Node Issue when blanking out data

I've created an Advanced Trigger in a custom version of the PR12 form. Using 1000-WF-ADD-VAR-SETUP, I add variables that correspond to all the fields on the form. The trigger kicks off a Processflow that sends any data changes to a custom approver InBasket. If the approver approves the changes, an AGS Node will submit the changes via an AGS Change call to the real PR12 form.

Everything was working upon initial testing. I could Add, Change and Delete data. Upon closer inspection of the Change calls, I noticed that blanking out data on the custom PR12 was not working. For example: if I wanted to eliminate the value in the "Payble To" field, I would highlight it and delete the data, then click the Change button, trigger would fire, work unit would show in Approver Inbasket, Approver would Approve, AGS call would complete but the data wouldn't change.

I determined it was due to the fact that the AGS Node was ignoring part of the AGS call because the data was blank. Various sources have suggested I pass %20 instead of a blank. So I tried this in the String Builder Wizard...worked perfect. Based on this, I decided to set my work unit variables %20 if they correspond to a blank field on my custom form. Down stream, when the AGS call executes, the %20 is converted to %2520.

Any idea why the Processflow AGS Node is doing this and how to get around it?