[Geschlossen] The translation progress cannot be saved beyond '69% complete'

Background of the issue:
I am trying to progress the Chinese translation of a long English article (versteckter Link) using the classic translation editor. The current status is '69% complete'. I added translations for some sentences, marked them as 'Translation is complete', and clicked the 'Save' button. After reloading the page, the translated sentences were not saved, and the status reverted to '69% complete'.
Please see my screencast versteckter Link (I couldn't upload it by the below "Click to Upload" button.

Symptoms:
The translation progress cannot be saved beyond '69% complete'. I encountered a 'WordPress database error Deadlock found when trying to get lock; try restarting transaction for query INSERT IGNORE INTO wp_options ( `option_name`, `option_value`, `autoload` ) VALUES ('wpml.WPMLTMSettingsProcessNewTranslatableFields.lock', '1753184716', 'no') /* LOCK */ made by require_once('wp-load.php'), require_once('wp-config.php'), require_once('wp-settings.php'), do_action('wp_loaded'), WP_Hook->do_action, WP_Hook->apply_filters, WPMLLIBWPHooks::WPMLLIBWP{closure}, WPMLFPPromise->resolve, WPMLFPRight->chain, WPMLFPRight->map, WPMLBackgroundTaskBackgroundTaskLoader->WPMLBackgroundTask{closure}, WPMLBackgroundTaskBackgroundTaskLoader->getSerializedTasks, WPMLFPFns::__callStatic, call_user_func_array, WPMLFPFns::WPMLFP{closure}, call_user_func_array, WPMLFPFns::WPMLFP{closure}, array_map, WPMLBackgroundTaskBackgroundTaskLoader->WPMLBackgroundTask{closure}, WPMLBackgroundTaskBackgroundTaskViewModel::get, WPMLUtilitiesLock->create, WPMLUtilitiesLock->create, WPMLUtilitiesLock->create, WPMLUtilitiesLock->create' in the error log.

Questions:
Why can't I save the translation progress beyond '69% complete'?
What does the 'WordPress database error Deadlock found' mean and how can I resolve it?
Should I clear any cache on the WPML Troubleshooting page?