I used timemachine to restore my project so that I could carefully reproduce this. Here's the scenario:
I've written a service in php and used the Data/Service wizard in FB to create my valueObject. The valueObject is called "Setting".
Now I'd like to add a parameter to one of the methods of my service object. I open up the php script for the service object in FB for PHP. I enter the new parameter for the function and save the file.
I immediately see that FB has created new valueObjects Setting1, _SuperSetting1 and _Setting1EntityMetadata.
So, I should be able to fix this be adding the required parameter to my data service call AS3. I add the parameter to the call. Now what? I notice that return type in my Data/Services tab has changed from "Setting" to "Setting1". So, I should reconfigure the return type for the function call. I right-click on the function, select Configure Return Type... and then set the return type back to the existing Setting.
What happens next is I get an error "Unhandled event loop exception java.lang.StackOverfolwError". After clicking Okay I'm told that I am recommended to exit the workbench.
I can't figure out how to fix this. I've gone in and manually edited the AS3 class for my service so that it's using the original Setting valueObject. I can now at least get the project to compile, and it is using Setting, not Setting1. But the Data/Services tab still shows that the funciton returns data type Setting1.