cache invalidation not performed when user changes their user id

get 2 different browsers up and running pointing at different nodes, change an external users email address on one of them (via accounts tool), paste the validation link into the same browsers as you changed the email, complete all fields and submit. then (in same browser) go to Account and make sure the user ID has been changed. on the other node either login as the external user & check the new user ID works or login as admin and user Users tool in admin workspace to check that the new user ID is associate with the external user.