MariaDB crashing

Hello, we are using MariaDB 10.1 in our project. Project is huge, as for me...we migrate from MySQL 5.6 to MariaDB 10.1 to have galera replication. So now, we have:
mysql1
haproxy ==>> mysql2

and mysql3 server for backups. This server not included in haproxy, just backups. And...after migration, everything was fine few weeks, then MariaDB 10.1 starts crashing, same error

170612 3:00:17 [ERROR] mysqld got signal 11 ;

And few days ago, MariaDB 10.2 released, I updated mysql3 server and mysql2, and again receive error. I attach error backtrase.

We are using 14.04.5 LTS
CPU: Intel(R) Xeon(R) CPU E5-1650 v3 @ 3.50GHz
RAM: 256Gb
2 SSD drives, 500Gb in software raid.

Same hardware on 3 servers.

Also i include my.cnf

Thank you.