After a reboot of our database machine it started hanging and MariaDB started crashing. (MariaDB was not upgraded just before reboot, 10.3.11 has been running on the machine prior to reboot)
I have attached some logs here from when it happens.

Since the reboot this has happened 4 times now (less than 24h after reboot).

Short log from Crash: https://pastebin.com/yWq36AKb
Full log from before crash (syslog): https://pastebin.com/MEZMNUbg

The server is running the latest patches from debian for buster and latest 10.3 version from sid repo (http://ftp.ddg.lth.se/mariadb/repo/10.3/debian).

Nov 25 19:46:38 db-01 mysqld[10328]: InnoDB: ###### Starts InnoDB Monitor for 30 secs to print diagnostic info:
Nov 25 19:46:38 db-01 mysqld[10328]: InnoDB: Pending reads 0, writes 0
Nov 25 19:47:08 db-01 mysqld[10328]: InnoDB: ###### Diagnostic info printed to the standard error stream
Nov 25 19:47:08 db-01 mysqld[10328]: 2018-11-25 19:47:08 0 [ERROR] [FATAL] InnoDB: Semaphore wait has lasted > 600 seconds. We intentionally crash the server because it appears to be hung.
Nov 25 19:47:08 db-01 mysqld[10328]: 181125 19:47:08 [ERROR] mysqld got signal 6 ;
Nov 25 19:47:08 db-01 mysqld[10328]: This could be because you hit a bug. It is also possible that this binary
Nov 25 19:47:08 db-01 mysqld[10328]: or one of the libraries it was linked against is corrupt, improperly built,
Nov 25 19:47:08 db-01 mysqld[10328]: or misconfigured. This error can also be caused by malfunctioning hardware.
Nov 25 19:47:08 db-01 mysqld[10328]: To report this bug, see https://mariadb.com/kb/en/reporting-bugs
Nov 25 19:47:08 db-01 mysqld[10328]: We will try our best to scrape up some info that will hopefully help
Nov 25 19:47:08 db-01 mysqld[10328]: diagnose the problem, but since we have already crashed,
Nov 25 19:47:08 db-01 mysqld[10328]: something is definitely wrong and this may fail.
Nov 25 19:47:08 db-01 mysqld[10328]: Server version: 10.3.11-MariaDB-1:10.3.11+maria~sid-log
Nov 25 19:47:08 db-01 mysqld[10328]: key_buffer_size=134217728
Nov 25 19:47:08 db-01 mysqld[10328]: read_buffer_size=2097152
Nov 25 19:47:08 db-01 mysqld[10328]: max_used_connections=527
Nov 25 19:47:08 db-01 mysqld[10328]: max_threads=1002
Nov 25 19:47:08 db-01 mysqld[10328]: thread_count=534
Nov 25 19:47:08 db-01 mysqld[10328]: It is possible that mysqld could use up to
Nov 25 19:47:08 db-01 mysqld[10328]: key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 6309679 K bytes of memory
Nov 25 19:47:08 db-01 mysqld[10328]: Hope that's ok; if not, decrease some variables in the equation.
Nov 25 19:47:08 db-01 mysqld[10328]: Thread pointer: 0x0
Nov 25 19:47:08 db-01 mysqld[10328]: Attempting backtrace. You can use the following information to find out
Nov 25 19:47:08 db-01 mysqld[10328]: where mysqld died. If you see no messages after this, something went
Nov 25 19:47:08 db-01 mysqld[10328]: terribly wrong...
Nov 25 19:47:08 db-01 mysqld[10328]: stack_bottom = 0x0 thread_stack 0x49000
Nov 25 19:47:09 db-01 mysqld[10328]: /usr/sbin/mysqld(my_print_stacktrace+0x2e)[0x556315543dbe]
Nov 25 19:47:09 db-01 mysqld[10328]: /usr/sbin/mysqld(handle_fatal_signal+0x5a5)[0x556314fe3055]
Nov 25 19:47:09 db-01 mysqld[10328]: /lib/x86_64-linux-gnu/libpthread.so.0(+0x128e0)[0x7f24ca1148e0]
Nov 25 19:47:09 db-01 mysqld[10328]: /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x10b)[0x7f24c9378f3b]
Nov 25 19:47:09 db-01 mysqld[10328]: /lib/x86_64-linux-gnu/libc.so.6(abort+0x151)[0x7f24c937a2f1]
Nov 25 19:47:09 db-01 mysqld[10328]: /usr/sbin/mysqld(+0xa15bb1)[0x5563152b1bb1]
Nov 25 19:47:09 db-01 mysqld[10328]: /usr/sbin/mysqld(+0x9c9f47)[0x556315265f47]
Nov 25 19:47:09 db-01 mysqld[10328]: /lib/x86_64-linux-gnu/libpthread.so.0(+0x7f2a)[0x7f24ca109f2a]
Nov 25 19:47:09 db-01 mysqld[10328]: /lib/x86_64-linux-gnu/libc.so.6(clone+0x3f)[0x7f24c943aedf]
Nov 25 19:47:09 db-01 mysqld[10328]: The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains
Nov 25 19:47:09 db-01 mysqld[10328]: information that should help you find out what is causing the crash.
Nov 25 19:50:29 db-01 systemd[1]: Started Session 52 of user suom1.
Nov 25 19:50:54 db-01 systemd[1]: mariadb.service: Main process exited, code=killed, status=6/ABRT
Nov 25 19:50:54 db-01 systemd[1]: mariadb.service: Failed with result 'signal'.
Nov 25 19:50:59 db-01 systemd[1]: mariadb.service: Service RestartSec=5s expired, scheduling restart.
Nov 25 19:50:59 db-01 systemd[1]: mariadb.service: Scheduled restart job, restart counter is at 2.
Nov 25 19:50:59 db-01 systemd[1]: Stopped MariaDB 10.3.11 database server.
Nov 25 19:50:59 db-01 systemd[1]: Starting MariaDB 10.3.11 database server...
Nov 25 19:51:00 db-01 mysqld[12343]: 2018-11-25 19:51:00 0 [Note] /usr/sbin/mysqld (mysqld 10.3.11-MariaDB-1:10.3.11+maria~sid-log) starting as process 12343 ...
Nov 25 19:51:00 db-01 mysqld[12343]: 2018-11-25 19:51:00 0 [Note] InnoDB: Using Linux native AIO
Nov 25 19:51:00 db-01 mysqld[12343]: 2018-11-25 19:51:00 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
Nov 25 19:51:00 db-01 mysqld[12343]: 2018-11-25 19:51:00 0 [Note] InnoDB: Uses event mutexes
Nov 25 19:51:00 db-01 mysqld[12343]: 2018-11-25 19:51:00 0 [Note] InnoDB: Compressed tables use zlib 1.2.11
Nov 25 19:51:00 db-01 mysqld[12343]: 2018-11-25 19:51:00 0 [Note] InnoDB: Number of pools: 1
Nov 25 19:51:00 db-01 mysqld[12343]: 2018-11-25 19:51:00 0 [Note] InnoDB: Using SSE2 crc32 instructions
Nov 25 19:51:00 db-01 mysqld[12343]: 2018-11-25 19:51:00 0 [Note] InnoDB: Initializing buffer pool, total size = 64G, instances = 64, chunk size = 128M
Nov 25 19:51:02 db-01 mysqld[12343]: 2018-11-25 19:51:02 0 [Note] InnoDB: Completed initialization of buffer pool
Nov 25 19:51:02 db-01 mysqld[12343]: 2018-11-25 19:51:02 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
Nov 25 19:51:02 db-01 mysqld[12343]: 2018-11-25 19:51:02 0 [Note] InnoDB: Starting crash recovery from checkpoint LSN=287284775094
Nov 25 19:51:02 db-01 mysqld[12343]: 2018-11-25 19:51:02 0 [Note] InnoDB: Starting final batch to recover 3 pages from redo log.
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] InnoDB: Last binlog file '/var/log/mysql/mariadb-bin.001469', position 450270
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] InnoDB: 128 out of 128 rollback segments are active.
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] InnoDB: Removed temporary tablespace data file: "ibtmp1"
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] InnoDB: Creating shared tablespace for temporary tables
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] InnoDB: Setting file './ibtmp1' size to 12 MB. Physically writing the file full; Please wait ...
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] InnoDB: File './ibtmp1' size is now 12 MB.
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] InnoDB: Waiting for purge to start
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] InnoDB: 10.3.11 started; log sequence number 287284775194; transaction id 316943429
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] InnoDB: Loading buffer pool(s) from /var/lib/mysql/ib_buffer_pool
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] Plugin 'FEEDBACK' is disabled.
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] Recovering after a crash using /var/log/mysql/mariadb-bin
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] Starting crash recovery...
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] Crash recovery finished.
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] Server socket created on IP: '::'.
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Warning] 'user' entry 'root@db-01' ignored in --skip-name-resolve mode.
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Warning] 'proxies_priv' entry '@% root@db-01' ignored in --skip-name-resolve mode.
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] Reading of all Master_info entries succeded
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] Added new Master_info '' to hash table
Nov 25 19:51:03 db-01 mysqld[12343]: 2018-11-25 19:51:03 0 [Note] /usr/sbin/mysqld: ready for connections.
Nov 25 19:51:03 db-01 mysqld[12343]: Version: '10.3.11-MariaDB-1:10.3.11+maria~sid-log' socket: '/var/run/mysqld/mysqld.sock' port: 3306 mariadb.org binary distribution
Nov 25 19:51:03 db-01 /etc/mysql/debian-start[12391]: Upgrading MySQL tables if necessary.
Nov 25 19:51:03 db-01 /etc/mysql/debian-start[12395]: /usr/bin/mysql_upgrade: the '--basedir' option is always ignored
Nov 25 19:51:03 db-01 /etc/mysql/debian-start[12395]: Looking for 'mysql' as: /usr/bin/mysql
Nov 25 19:51:03 db-01 /etc/mysql/debian-start[12395]: Looking for 'mysqlcheck' as: /usr/bin/mysqlcheck
Nov 25 19:51:03 db-01 /etc/mysql/debian-start[12395]: This installation of MySQL is already upgraded to 10.3.11-MariaDB, use --force if you still need to run mysql_upgrade
Nov 25 19:51:03 db-01 /etc/mysql/debian-start[12404]: Checking for insecure root accounts.
Nov 25 19:51:03 db-01 /etc/mysql/debian-start[12409]: Triggering myisam-recover for all MyISAM tables and aria-recover for all Aria tables
Nov 25 19:51:03 db-01 systemd[1]: Started MariaDB 10.3.11 database server.
Nov 25 19:51:33 db-01 mysqld[12343]: 2018-11-25 19:51:33 0 [Note] InnoDB: Buffer pool(s) load completed at 181125 19:51:33