RoundCube & MySQLi error while backup operation in Directadmin

[mbsmt]

I have multiple servers with DirectAdmin. All of these servers have backup schedules and all of these tasks are working well, except one.
This is the error I am receiving while backup operation:

RoundCube Backup Error:
Warning: mysqli::__construct(): Unexpected server respose while doing caching_sha2 auth: 109 in /usr/local/directadmin/scripts/backup_roundcube.php on line 121

Warning: mysqli::__construct(): MySQL server has gone away in /usr/local/directadmin/scripts/backup_roundcube.php on line 121

Warning: mysqli::__construct(): (HY000/2006): MySQL server has gone away in /usr/local/directadmin/scripts/backup_roundcube.php on line 121
Failed to connect to MySQL: (2006) MySQL server has gone away

May you help me to solve this issue please?

 

[floyd]

For some reason mysql is stopping or restarting during that time. Do you have plenty of memory? What does the mysql log say during that time?