Debug info: ORA-00001: unique constraint (MOODLE20.M_BLOCPOSI_BLOCONPAGSUB_UIX) violated
INSERT INTO m_block_positions (region,weight,blockinstanceid,contextid,pagetype,subpage,visible) VALUES (:region,:weight,:blockinstanceid,:contextid,:pagetype,:subpage,:visible) RETURNING id INTO :oracle_id
[array (
'region' => 'side-pre',
'weight' => -1,
'blockinstanceid' => '4',
'contextid' => '121',
'pagetype' => 'course-view-topics',
'subpage' => '',
'visible' => '1',
)]
Stack trace:

• line 394 of /lib/dml/moodle_database.php: dml_write_exception thrown
• line 268 of /lib/dml/oci_native_moodle_database.php: call to moodle_database->query_end()
• line 1147 of /lib/dml/oci_native_moodle_database.php: call to oci_native_moodle_database->query_end()
• line 1190 of /lib/dml/oci_native_moodle_database.php: call to oci_native_moodle_database->insert_record_raw()
• line 752 of /lib/blocklib.php: call to oci_native_moodle_database->insert_record()
• line 1383 of /lib/blocklib.php: call to block_manager->reposition_block()
• line 1041 of /lib/blocklib.php: call to block_manager->process_url_move()
• line 1178 of /lib/pagelib.php: call to block_manager->process_url_actions()
• line 702 of /lib/pagelib.php: call to moodle_page->starting_output()
• line 600 of /lib/outputrenderers.php: call to moodle_page->set_state()
• line 196 of /course/view.php: call to core_renderer->header()