Adding the assign didn't help so I moved all of the libraries in to a temporary folder and moved them back one by one. It turns out the graphics library was making it hang. Also, even with just the afa_system_lib present, the 3.9 version of workbench.library doesn't seem to take effect as Amidock doesn't load and my dialogs (e.g. Execute Command) all change back to the 3.1 versions :-?
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moto