[Closed] wpml settings page doesn't load

Background of the issue:
I was attempting to load the WPML settings page in the WordPress admin area.

php slow log:
[28-May-2024 18:59:17] [pool www] pid 470460
script_filename = /wp-admin/admin.php
[0x0000ffffbaa12c10] mysqli_query() /wp-includes/class-wpdb.php:2349
[0x0000ffffbaa12ba0] _do_query() /wp-includes/class-wpdb.php:2263
[0x0000ffffbaa12ac0] query() /wp-includes/class-wpdb.php:3031
[0x0000ffffbaa129e0] get_var() /wp-content/plugins/sitepress-multilingual-cms/classes/translate_link_targets/class-wpml-translate-link-targets-in-posts-global.php:10
[0x0000ffffbaa12950] get_number_to_be_fixed() /wp-content/plugins/sitepress-multilingual-cms/classes/menu/mcsetup/class-wpml-translate-link-targets-ui.php:33
[0x0000ffffbaa12830] render_content() /wp-content/plugins/sitepress-multilingual-cms/classes/menu/mcsetup/class-wpml-tm-mcs-section-ui.php:38
[0x0000ffffbaa127b0] render() /wp-content/plugins/sitepress-multilingual-cms/menu/wpml-tm-menus-settings.php:665
[0x0000ffffbaa12690] build_content_mcs() /wp-content/plugins/sitepress-multilingual-cms/menu/wpml-tm-menus.class.php:101
[0x0000ffffbaa125d0] build_content() /wp-content/plugins/sitepress-multilingual-cms/menu/wpml-tm-menus.class.php:119
[0x0000ffffbaa12570] render_items() /wp-content/plugins/sitepress-multilingual-cms/menu/wpml-tm-menus-settings.php:95
[0x0000ffffbaa12510] render_main() /wp-content/plugins/sitepress-multilingual-cms/menu/wpml-tm-menus.class.php:27
[0x0000ffffbaa12490] display_main() /wp-content/plugins/sitepress-multilingual-cms/classes/class-wpml-translation-management.php:406
[0x0000ffffbaa12410] settings_page() /wp-includes/class-wp-hook.php:324
[0x0000ffffbaa12330] apply_filters() /wp-includes/class-wp-hook.php:348
[0x0000ffffbaa122c0] do_action() /wp-includes/plugin.php:517
[0x0000ffffbaa121e0] do_action() /wp-admin/admin.php:259

mysql slow log:
# Time: 2024-05-28T18:59:16.816636Z
# Query_time: 60.589167 Lock_time: 0.000001 Rows_sent: 20 Rows_examined: 15892065
SET timestamp=1716922696;
SELECT SQL_CALC_FOUND_ROWS DISTINCT meta_key FROM wp_postmeta WHERE 1=1 AND meta_key NOT IN('_edit_last','_edit_lock','_wp_page_template','_wp_attachment_metadata','_icl_translator_note','_alp_processed','_pingme','_encloseme','_icl_lang_duplicate_of','_wpml_media_duplicate','wpml_media_processed','_wpml_media_featured','_thumbnail_id') AND meta_key NOT LIKE '_%' LIMIT 20 OFFSET 0;

Symptoms:
The settings page failed to load, resulting in a 504 timeout error after 1 minute. The PHP slow log indicates a bottleneck at several database query functions, and the MySQL slow log shows a query taking over 60 seconds with a large number of rows examined.

Questions:
What could be causing the 504 timeout error when trying to load the WPML settings page?
How can I resolve the slow query performance as indicated in the MySQL slow log?