Ok, I think I solved it. Apart from removing everything that has to do with the sandbox-store, I had to remove (defstore *scratch-store* :memory) in stores.lisp. For me it was not obvious that I had to do that. Moreover it says in stores.lisp that the last defstore is the standard one. I interpret that as the one which will be the selected one. Consequently, the scratch-store should be ignored since it comes before the prevalence-store. Can you please add that to the README file?
Another thing that is strange is that I have to restart slime in order for the change, i.e. commenting out the scratch-store, to have any effect. Should it not be enough by invoking (asdf:operate 'asdf:load-op :weblocks-demo)?
Thanks,
Mikael