I faced a similar problem, when i tried to delete an unused process model via MWS admin console,i ran into socket timeout exceptions. After restart of IS and MWS, i was able to delete the model using MWS admin console.
One other thing you can notice is, the delete button will be active for an unused model, letting you delete via MWS admin console, which is not the case for a used process model.
As i mentioned before, you have to follow the instructions mentioned in wM Monitor user guide, to get rid of used one.
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