General help

Hey, I Migrated a website from cloud to local server and now the complete migration is done, I am getting this error on login, 

This is the stacktrace that I get when I turned on the developer mode.

SELECT cm.*, m.name, md.name AS modname 
              FROM {course_modules} cm
                   JOIN {modules} md ON md.id = cm.module
                   JOIN {assign} m ON m.id = cm.instance
                   
             WHERE m.id = :instance AND md.name = :modulename
                   
[array (
  'instance' => '1',
  'modulename' => 'assign',
)]
Error code: multiplerecordsfound
* line 1581 of /lib/dml/moodle_database.php: dml_multiple_records_exception thrown
* line 1348 of /lib/datalib.php: call to moodle_database->get_record_sql()
* line 8483 of /mod/assign/locallib.php: call to get_coursemodule_from_instance()
* line 8524 of /mod/assign/locallib.php: call to assign::allocate_unique_ids()
* line 8472 of /mod/assign/locallib.php: call to assign::get_uniqueid_for_user_static()
* line 4467 of /mod/assign/locallib.php: call to assign->get_uniqueid_for_user()
* line 1890 of /mod/assign/locallib.php: call to assign->fullname()
* line 2060 of /mod/assign/locallib.php: call to assign->get_submission_info_for_participants()
* line 1889 of /mod/assign/lib.php: call to assign->get_participant()
* line 7684 of /lib/moodlelib.php: call to mod_assign_core_calendar_provide_event_action()
* line 255 of /calendar/classes/local/event/container.php: call to component_callback()
* line 42 of /calendar/classes/local/event/factories/event_factory.php: call to core_calendar\local\event\container::apply_component_provide_event_action()
* line 197 of /calendar/classes/local/event/factories/event_abstract_factory.php: call to core_calendar\local\event\factories\event_factory->apply_component_action()
* line 357 of /calendar/classes/local/event/data_access/event_vault.php: call to core_calendar\local\event\factories\event_abstract_factory->create_instance()
* line 177 of /calendar/classes/local/event/data_access/event_vault.php: call to core_calendar\local\event\data_access\event_vault->transform_from_database_record()
* line 231 of /calendar/classes/local/event/data_access/event_vault.php: call to core_calendar\local\event\data_access\event_vault->get_events()
* line 147 of /calendar/classes/local/api.php: call to core_calendar\local\event\data_access\event_vault->get_action_events_by_timesort()
* line 449 of /calendar/externallib.php: call to core_calendar\local\api::get_action_events_by_timesort()
* line 228 of /lib/externallib.php: call to core_calendar_external::get_calendar_action_events_by_timesort()
* line 59 of /lib/ajax/service.php: call to external_api::call_external_function()
SELECT cm.*, m.name, md.name AS modname 
              FROM {course_modules} cm
                   JOIN {modules} md ON md.id = cm.module
                   JOIN {assign} m ON m.id = cm.instance
                   
             WHERE m.id = :instance AND md.name = :modulename
                   
[array (
  'instance' => '1',
  'modulename' => 'assign',
)]
Error code: multiplerecordsfound
* line 1581 of /lib/dml/moodle_database.php: dml_multiple_records_exception thrown
* line 1348 of /lib/datalib.php: call to moodle_database->get_record_sql()
* line 8483 of /mod/assign/locallib.php: call to get_coursemodule_from_instance()
* line 8524 of /mod/assign/locallib.php: call to assign::allocate_unique_ids()
* line 8472 of /mod/assign/locallib.php: call to assign::get_uniqueid_for_user_static()
* line 4467 of /mod/assign/locallib.php: call to assign->get_uniqueid_for_user()
* line 1890 of /mod/assign/locallib.php: call to assign->fullname()
* line 2060 of /mod/assign/locallib.php: call to assign->get_submission_info_for_participants()
* line 1889 of /mod/assign/lib.php: call to assign->get_participant()
* line 7684 of /lib/moodlelib.php: call to mod_assign_core_calendar_provide_event_action()
* line 255 of /calendar/classes/local/event/container.php: call to component_callback()
* line 42 of /calendar/classes/local/event/factories/event_factory.php: call to core_calendar\local\event\container::apply_component_provide_event_action()
* line 197 of /calendar/classes/local/event/factories/event_abstract_factory.php: call to core_calendar\local\event\factories\event_factory->apply_component_action()
* line 357 of /calendar/classes/local/event/data_access/event_vault.php: call to core_calendar\local\event\factories\event_abstract_factory->create_instance()
* line 177 of /calendar/classes/local/event/data_access/event_vault.php: call to core_calendar\local\event\data_access\event_vault->transform_from_database_record()
* line 231 of /calendar/classes/local/event/data_access/event_vault.php: call to core_calendar\local\event\data_access\event_vault->get_events()
* line 147 of /calendar/classes/local/api.php: call to core_calendar\local\event\data_access\event_vault->get_action_events_by_timesort()
* line 449 of /calendar/externallib.php: call to core_calendar\local\api::get_action_events_by_timesort()
* line 228 of /lib/externallib.php: call to core_calendar_external::get_calendar_action_events_by_timesort()
* line 59 of /lib/ajax/service.php: call to external_api::call_external_function()

I get this is some issue with the assignment module, but I dont know what.

Thanks alot. 
Waleed