Tente isto
$ heroku run rails console
irb(main)> ActiveRecord::Base.connection.tables.each { |t| ActiveRecord::Base.connection.reset_pk_sequence!(t) }
Fonte:https://stackoverflow.com/a/15108735/3034747
$ heroku run rails console
irb(main)> ActiveRecord::Base.connection.tables.each { |t| ActiveRecord::Base.connection.reset_pk_sequence!(t) }