MariaDB 10.1.14 crashes while optimizing table & replication

Given a MariaDB galera cluster with 3 nodes, with one node being additionally a two-source async replaction slave (replication masters: mysqld 5.1.72-1 and mysqld 5.5.47-0). During execution of some OPTIMIZE TABLE commands on innoDB tables (while active sync and async replications), this node crashed with follwing output:

[...]
2016-07-07 10:26:06 140210748758784 [Note] InnoDB: Online DDL : Start merge-sorting index `reporting_2_index` (8 / 9), estimated cost : 4.4211
2016-07-07 10:26:06 140210748758784 [Note] InnoDB: Online DDL : merge-sorting has estimated 115 runs
2016-07-07 10:26:50 140210748758784 [Note] InnoDB: Online DDL : End of merge-sorting index `reporting_2_index` (8 / 9)
2016-07-07 10:26:50 140210748758784 [Note] InnoDB: Online DDL : Start building index `reporting_2_index` (8 / 9), estimated cost : 6.6316
2016-07-07 10:28:14 140210748758784 [Note] InnoDB: Online DDL : End of building index `reporting_2_index` (8 / 9)
2016-07-07 10:28:14 140210748758784 [Note] InnoDB: Online DDL : Completed
2016-07-07 10:28:14 140210748758784 [Note] InnoDB: Online DDL : Start merge-sorting index `itemKennwerte` (9 / 9), estimated cost : 4.1474
2016-07-07 10:28:14 140210748758784 [Note] InnoDB: Online DDL : merge-sorting has estimated 102 runs
2016-07-07 10:28:44 140210748758784 [Note] InnoDB: Online DDL : End of merge-sorting index `itemKennwerte` (9 / 9)
2016-07-07 10:28:44 140210748758784 [Note] InnoDB: Online DDL : Start building index `itemKennwerte` (9 / 9), estimated cost : 6.2211
2016-07-07 10:30:00 140210748758784 [Note] InnoDB: Online DDL : End of building index `itemKennwerte` (9 / 9)
2016-07-07 10:30:00 140210748758784 [Note] InnoDB: Online DDL : Completed
2016-07-07 10:30:41 7f85579bbb00 InnoDB: Assertion failure in thread 140210677201664 in file lock0lock.cc line 4624
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to http://bugs.mysql.com.
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: http://dev.mysql.com/doc/refman/5.6/en/forcing-innodb-recovery.html
InnoDB: about forcing recovery.
160707 10:30:41 [ERROR] mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.

To report this bug, see https://mariadb.com/kb/en/reporting-bugs

We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.

Server version: 10.1.14-MariaDB
key_buffer_size=524288
read_buffer_size=131072
max_used_connections=3
max_threads=153
thread_count=3
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 336553 K bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x0x7f85085ac008
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0x7f85579ba8d0 thread_stack 0x48400
mysqld(my_print_stacktrace+0x2e)[0x7f855ca011be]
mysqld(handle_fatal_signal+0x38d)[0x7f855c52cf0d]
/lib64/libpthread.so.0(+0xf100)[0x7f855bb4b100]
/lib64/libc.so.6(gsignal+0x37)[0x7f8559ea45f7]
/lib64/libc.so.6(abort+0x148)[0x7f8559ea5ce8]
addr2line: 'mysqld': No such file
mysqld(+0x37afc9)[0x7f855c2f6fc9]
mysqld(+0x7662da)[0x7f855c6e22da]
mysqld(+0x7cd121)[0x7f855c749121]
mysqld(+0x7cdc86)[0x7f855c749c86]
mysqld(+0x7d1a56)[0x7f855c74da56]
mysqld(+0x7d1ea8)[0x7f855c74dea8]
mysqld(+0x7dec00)[0x7f855c75ac00]
mysqld(+0x7308ff)[0x7f855c6ac8ff]
mysqld(_ZN7handler12ha_write_rowEPh+0x2ef)[0x7f855c536eaf]
mysqld(_ZN14Rows_log_event9write_rowEP14rpl_group_infob+0x16d)[0x7f855c60919d]
mysqld(_ZN20Write_rows_log_event11do_exec_rowEP14rpl_group_info+0x7d)[0x7f855c6095ad]
mysqld(_ZN14Rows_log_event14do_apply_eventEP14rpl_group_info+0x31c)[0x7f855c5fc5cc]
mysqld(_Z26apply_event_and_update_posP9Log_eventP3THDP14rpl_group_infoP19rpl_parallel_thread+0x1e1)[0x7f855c3366d1]
mysqld(handle_slave_sql+0x259b)[0x7f855c33a08b]
/lib64/libpthread.so.0(+0x7dc5)[0x7f855bb43dc5]
/lib64/libc.so.6(clone+0x6d)[0x7f8559f65ced]

Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query (0x0):
Connection ID (thread ID): 430
Status: NOT_KILLED

Optimizer switch: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,engine_condition_pushdown=off,index_condition_pushdown=on,derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on,extended_keys=on,exists_to_in=on

The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains
information that should help you find out what is causing the crash.