I got the following when trying to restore a backup of a course on the same site.
I was admin with default settings/capabilities restoring the course as a new course in the misc category.
The course itself has one single file upload with advanced grading rubric.

error/exception 'dml_write_exception' with message 'Error writing to database' in /private/var/www/integration/lib/dml/moodle_database.php:397

Stack trace:
#0 /private/var/www/integration/lib/dml/pgsql_native_moodle_database.php(232): moodle_database->query_end(false)
#1 /private/var/www/integration/lib/dml/pgsql_native_moodle_database.php(781): pgsql_native_moodle_database->query_end(false)
#2 /private/var/www/integration/lib/dml/pgsql_native_moodle_database.php(833): pgsql_native_moodle_database->insert_record_raw('grading_instanc...', Array, true, false)
#3 /private/var/www/integration/backup/moodle2/restore_stepslib.php(2000): pgsql_native_moodle_database->insert_record('grading_instanc...', Object(stdClass))
#4 /private/var/www/integration/backup/util/plan/restore_structure_step.class.php(131): restore_activity_grading_structure_step->process_grading_instance(Array)
#5 /private/var/www/integration/backup/util/helper/restore_structure_parser_processor.class.php(103): restore_structure_step->process(Array)
#6 /private/var/www/integration/backup/util/xml/parser/processors/grouped_parser_processor.class.php(125): restore_structure_parser_processor->dispatch_chunk(Array)
#7 /private/var/www/integration/backup/util/helper/restore_structure_parser_processor.class.php(91): grouped_parser_processor->postprocess_chunk(Array)
#8 /private/var/www/integration/backup/util/xml/parser/processors/simplified_parser_processor.class.php(148): restore_structure_parser_processor->postprocess_chunk(Array)
#9 /private/var/www/integration/backup/util/xml/parser/processors/progressive_parser_processor.class.php(92): simplified_parser_processor->process_chunk(Array)
#10 /private/var/www/integration/backup/util/xml/parser/progressive_parser.class.php(169): progressive_parser_processor->receive_chunk(Array)
#11 /private/var/www/integration/backup/util/xml/parser/progressive_parser.class.php(212): progressive_parser->publish(Array)
#12 [internal function]: progressive_parser->start_tag(Resource id #2369, 'fillings', Array)
#13 /private/var/www/integration/backup/util/xml/parser/progressive_parser.class.php(158): xml_parse(Resource id #2369, '<?xml version="...', 0)
#14 /private/var/www/integration/backup/util/xml/parser/progressive_parser.class.php(137): progressive_parser->parse('<?xml version="...', false)
#15 /private/var/www/integration/backup/util/plan/restore_structure_step.class.php(105): progressive_parser->process()
#16 /private/var/www/integration/backup/util/plan/base_task.class.php(153): restore_structure_step->execute()
#17 /private/var/www/integration/backup/moodle2/restore_activity_task.class.php(182): base_task->execute()
#18 /private/var/www/integration/backup/util/plan/base_plan.class.php(148): restore_activity_task->execute()
#19 /private/var/www/integration/backup/util/plan/restore_plan.class.php(157): base_plan->execute()
#20 /private/var/www/integration/backup/controller/restore_controller.class.php(302): restore_plan->execute()
#21 /private/var/www/integration/backup/util/ui/restore_ui.class.php(144): restore_controller->execute_plan()
#22 /private/var/www/integration/backup/restore.php(46): restore_ui->execute() #23

Unknown macro: {main}

parse('process() #16 /private/var/www/integration/backup/util/plan/base_task.class.php(153): restore_structure_step->execute() #17 /private/var/www/integration/backup/moodle2/restore_activity_task.class.php(182): base_task->execute() #18 /private/var/www/integration/backup/util/plan/base_plan.class.php(148): restore_activity_task->execute() #19 /private/var/www/integration/backup/util/plan/restore_plan.class.php(157): base_plan->execute() #20 /private/var/www/integration/backup/controller/restore_controller.class.php(302): restore_plan->execute() #21 /private/var/www/integration/backup/util/ui/restore_ui.class.php(144): restore_controller->execute_plan() #22 /private/var/www/integration/backup/restore.php(46): restore_ui->execute() #23

">More information about this error

Stack trace:
line 49 of /backup/restore.php: moodle_exception thrown