You will probably need to clean your database between some (or each) of yours test cases/scenarios.
When running Capybara+PhantomJS, using table truncation is preferred since transactions are not shared between the test process and the browser process.
This means that you need to authorize the app account to truncate the appropriate tables. In the database setup transactions, this can be done for the accounts
table with:
run "GRANT TRUNCATE ON account_password_hashes TO #{user}"
Make sure that you do the same for each table created by the Rodauth features you have enabled, e.g. here for the disallow_password_reuse
feature: