Sorry I have the same problem and I don't understand how you solved it?

Moodle 3.8.2+ (Build: 20200506)

Default exception handler: Si è verificato un errore durante la lettura del database Debug: MySQL server has gone away

SELECT * FROM mdl_task_scheduled WHERE classname = ?

[array (

  0 => '\\tool_analytics\\task\\predict_models',

)]

Error code: dmlreadexception

* line 486 of /lib/dml/moodle_database.php: dml_read_exception thrown

* line 1247 of /lib/dml/mysqli_native_moodle_database.php: call to moodle_database->query_end()

* line 1587 of /lib/dml/moodle_database.php: call to mysqli_native_moodle_database->get_records_sql()

* line 1559 of /lib/dml/moodle_database.php: call to moodle_database->get_record_sql()

* line 1538 of /lib/dml/moodle_database.php: call to moodle_database->get_record_select()

* line 682 of /lib/classes/task/manager.php: call to moodle_database->get_record()

* line 229 of /lib/cronlib.php: call to core\task\manager::scheduled_task_failed()

* line 119 of /lib/cronlib.php: call to cron_run_inner_scheduled_task()

* line 73 of /lib/cronlib.php: call to cron_run_scheduled_tasks()

* line 61 of /admin/cli/cron.php: call to cron_run()

PHP Fatal error:  Uncaught coding_exception: E' stato rilevato un errore di programmazione, deve essere sistemato da un programmatore: A lock was created but not released at:

/var/www/html/lib/classes/task/manager.php on line 554

 $factory = \core\lock\lock_config::get_lock_factory('type');

 $lock = $factory->get_lock(Resource id #682);

 $lock->release();  // Locks must ALWAYS be released like this.

 in /var/www/html/lib/classes/lock/lock.php:117

Stack trace:

#0 [internal function]: core\lock\lock->__destruct()

#1 {main}

  thrown in /var/www/html/lib/classes/lock/lock.php on line 117