There seems to be a bug which stops the last stack of the state from being removed if you have the "state removal type" set to "single" in the plugin parameters.
Using either the "remove state" event function or the plugin's script for decreasing states will not remove the last stack. Only the "Recover All" function will remove the final stack. Hoping this can be fixed soon.
I can send a project file with the bug if you have a contact email.