Debug info: Duplicate entry '0' for key 'mdl_quizatte_uni_uix'

INSERT INTO mdl_quiz_attempts (uniqueid,userid,sumgrades,timestart,timefinish,timemodified,layout,preview,quiz,attempt) VALUES(?,?,?,?,?,?,?,?,?,?)

[array (

0 => 0,

1 => '5',

2 => '1.00000',

3 => 1287061174,

4 => 1287061181,

5 => 1287061181,

6 => '1,0',

7 => '0',

8 => 66,

9 => '1',

)]

Stack trace:

line 396 of /lib/dml/moodle_database.php: dml_write_exception thrown

line 878 of /lib/dml/mysqli_native_moodle_database.php: call to moodle_database->query_end()

line 920 of /lib/dml/mysqli_native_moodle_database.php: call to mysqli_native_moodle_database->insert_record_raw()

line 291 of /mod/quiz/backup/moodle2/restore_quiz_stepslib.php: call to mysqli_native_moodle_database->insert_record()

line 300 of /mod/quiz/backup/moodle2/restore_quiz_stepslib.php: call to restore_quiz_activity_structure_step->process_quiz_attempt()

line 131 of /backup/util/plan/restore_structure_step.class.php: call to restore_quiz_activity_structure_step->process_quiz_attempt_legacy()

...

...