bt full (for brevity):

#0  0x00007fcff47f40b1 in pthread_kill () from /usr/lib/libpthread.so.0
No symbol table info available.
#1  0x0000000000941cbf in my_write_core (sig=6) at /media/Tintin/Work/code/percona-xtradb-cluster/pxc56/Percona-Server/mysys/stacktrace.c:422
No locals.
#2  0x00000000006d83ec in handle_fatal_signal (sig=6) at /media/Tintin/Work/code/percona-xtradb-cluster/pxc56/Percona-Server/sql/signal_handler.cc:254
        curr_time = <optimized out>
        thrs = <optimized out>
        mins = <optimized out>
        hrs_buf = "20"
        hrs = <optimized out>
        mins_buf = "35"
        secs_buf = "34"
        tmins = <optimized out>
        secs = <optimized out>
        thd = 0x7fcfcc0009a0
#3  <signal handler called>
No symbol table info available.
#4  0x00007fcff2b843d9 in raise () from /usr/lib/libc.so.6
No symbol table info available.
#5  0x00007fcff2b857d8 in abort () from /usr/lib/libc.so.6
No symbol table info available.
#6  0x00007fcff2b7d506 in __assert_fail_base () from /usr/lib/libc.so.6
No symbol table info available.
#7  0x00007fcff2b7d5b2 in __assert_fail () from /usr/lib/libc.so.6
No symbol table info available.
#8  0x00000000007e7bc5 in trans_check_state (thd=thd@entry=0x7fcfcc0009a0) at /media/Tintin/Work/code/percona-xtradb-cluster/pxc56/Percona-Server/sql/transaction.cc:42
        xa_state = XA_NOTR
        _db_stack_frame_ = {
          func = 0xc63cee "trans_rollback", 
          file = 0xc63db8 "/media/Tintin/Work/code/percona-xtradb-cluster/pxc56/Percona-Server/sql/transaction.cc", 
          level = 2147483651, 
          prev = 0x7fcff4a9bee0
        }
        __PRETTY_FUNCTION__ = "bool trans_check_state(THD*)"
#9  0x00000000007e83a3 in trans_rollback (thd=thd@entry=0x7fcfcc0009a0) at /media/Tintin/Work/code/percona-xtradb-cluster/pxc56/Percona-Server/sql/transaction.cc:347
        res = <optimized out>
        _db_stack_frame_ = {
          func = 0xc07539 "wsrep_replication_process", 
          file = 0xc071f0 "/media/Tintin/Work/code/percona-xtradb-cluster/pxc56/Percona-Server/sql/wsrep_thd.cc", 
          level = 2147483650, 
          prev = 0x7fcff4a9d680
        }
        buf1 = "\001-\000\314\317\177\000\000\021-\000\314\317\177\000\000\177-\000\314\317\177\000\000\001-\000\314\317\177\000\000\177-\000\314\317\177", '\000' <repeats 42 times>, "\360ɩ\364\004\000\000\000@E\000\314\317\177\000\000\360\277\251\364\317\177\000\000h\346\251\364\317\177\000\000\220\277\251\364\317\177\000\000(\023\275\000\000\000\000\000\377\377\377\377\377\377\377\377\t\017\275\000\000\000\000\000\340\277\251\364\317\177\000\000s%\275\000\000\000\000\000\377\377\377\377\000\000\000\000p\001\000\000\002\000\000\000\b\257\021\314\317\177\000\000P$\000\314\317\177\000\000\001-\000\314\317\177\000\000\300p\300"...
        buf2 = "\002\000\000\200\317\177\000\000\200֩\364\317\177\000\000\060\300\251\364\317\177\000\000\240\t\000\314\317\177\000\000\001-\000\314\317\177\000\000\340\300\251\364\317\177\000\000@\300\251\364\317\177\000\000\016\306q\000\000\000\000\000\220\300\251\364\317\177\000\000\256\337q\000\000\000\000\000\002\020\000\000\000\000\000\000\300p\300\000\000\000\000\000\060\301\251\364\317\177\000\000\340\300\251\364\317\177\000\000\000\301\251\364\317\177\000\000\300p\300\000\000\000\000\000\030m\300\000\000\000\000\000&\001\000\000\000\000\000\000\320\300\251\364\317\177\000\000\376\337q", '\000' <repeats 13 times>, "\240\t\000\314\317\177\000\000\001-\000\314\317\177", '\000' <repeats 11 times>, "ũ\364\317\177\000\000\260\000\000\000\000\000\000\000"...
#10 0x0000000000638f5e in wsrep_rollback (thd=thd@entry=0x7fcfcc0009a0, global_seqno=<optimized out>) at /media/Tintin/Work/code/percona-xtradb-cluster/pxc56/Percona-Server/sql/wsrep_applier.cc:299
        __FUNCTION__ = "wsrep_rollback"
        rcode = <optimized out>
#11 0x000000000063995b in wsrep_commit_cb (ctx=ctx@entry=0x7fcfcc0009a0, meta=meta@entry=0x7fcff4a9c9f0, exit=exit@entry=0x7fcff4a9c500, commit=commit@entry=false) at /media/Tintin/Work/code/percona-xtradb-cluster/pxc56/Percona-Server/sql/wsrep_applier.cc:329
        thd = 0x7fcfcc0009a0
        __PRETTY_FUNCTION__ = "wsrep_cb_status_t wsrep_commit_cb(void*, const wsrep_trx_meta_t*, wsrep_bool_t*, bool)"
        rcode = <optimized out>
#12 0x00007fcff20d6d5d in apply_trx_ws (recv_ctx=recv_ctx@entry=0x7fcfcc0009a0, apply_cb=0x6397cb <wsrep_apply_cb(void*, void const*, unsigned long, wsrep_trx_meta const*)>, commit_cb=0x6398ed <wsrep_commit_cb(void*, wsrep_trx_meta const*, bool*, bool)>, trx=..., meta=...) at galera/src/replicator_smm.cpp:61
        unused = 160
        rcode = <optimized out>
        err = <optimized out>
        e = @0x7fcfcc36ab70: {
          <gu::Exception> = {
            <std::exception> = {<No data fields>}, 
            members of gu::Exception: 
            msg = "Failed to apply app buffer: seqno: 176, status: 1\n\t at galera/src/trx_handle.cpp:apply():333", 
            err = 1
          }, <No data fields>}
        attempts = 1
        __FUNCTION__ = "apply_trx_ws"
#13 0x00007fcff20d99b0 in galera::ReplicatorSMM::apply_trx (this=this@entry=0x32e0bd0, recv_ctx=recv_ctx@entry=0x7fcfcc0009a0, trx=trx@entry=0x7fcfcc1b65d0) at galera/src/replicator_smm.cpp:470
        ao = {
          trx_ = @0x7fcfcc1b65d0
        }
        co = {
          trx_ = @0x7fcfcc1b65d0, 
          mode_ = galera::ReplicatorSMM::CommitOrder::NO_OOOC
        }
        exit_loop = false
        rcode = <optimized out>
        __FUNCTION__ = "apply_trx"
        meta = {
          gtid = {
            uuid = {
              data = "&=\251\354+\242\021\343\277=ޫ\362h\232%"
            }, 
            seqno = 176
          }, 
          depends_on = 175
        }
#14 0x00007fcff20dbefe in galera::ReplicatorSMM::process_trx (this=0x32e0bd0, recv_ctx=0x7fcfcc0009a0, trx=0x7fcfcc1b65d0) at galera/src/replicator_smm.cpp:1242
        __FUNCTION__ = "process_trx"
#15 0x00007fcff20baa19 in galera::GcsActionSource::dispatch (this=this@entry=0x32e11b0, recv_ctx=recv_ctx@entry=0x7fcfcc0009a0, act=..., exit_loop=@0x7fcff4a9d310: false) at galera/src/gcs_action_source.cpp:118
        trx = {
          trx_ = 0x7fcfcc1b65d0
        }
        __FUNCTION__ = "dispatch"
#16 0x00007fcff20bb90c in galera::GcsActionSource::process (this=0x32e11b0, recv_ctx=0x7fcfcc0009a0, exit_loop=@0x7fcff4a9d310: false) at galera/src/gcs_action_source.cpp:177
        act = {
          buf = 0x7fcfe403f544, 
          size = 330, 
          seqno_g = 176, 
          seqno_l = 185, 
          type = GCS_ACT_TORDERED
        }
        rc = 330
#17 0x00007fcff20dc11b in galera::ReplicatorSMM::async_recv (this=0x32e0bd0, recv_ctx=0x7fcfcc0009a0) at galera/src/replicator_smm.cpp:346
        rc = <optimized out>
        __FUNCTION__ = "async_recv"
        exit_loop = false
        retval = WSREP_OK
#18 0x00007fcff20ecc68 in galera_recv (gh=<optimized out>, recv_ctx=<optimized out>) at galera/src/wsrep_provider.cpp:207
        repl = <optimized out>
        __FUNCTION__ = "galera_recv"
#19 0x0000000000639d10 in wsrep_replication_process (thd=0x7fcfcc0009a0) at /media/Tintin/Work/code/percona-xtradb-cluster/pxc56/Percona-Server/sql/wsrep_thd.cc:264
        rcode = <optimized out>
        _db_stack_frame_ = {
          func = 0xd7f2d0 "?func", 
          file = 0xd7f2d6 "?file", 
          level = 2147483649, 
          prev = 0x0
        }
        shadow = {
          options = 2147748608, 
          wsrep_exec_mode = REPL_RECV, 
          vio = 0x0, 
          tx_isolation = 2
        }
#20 0x0000000000624a3e in start_wsrep_THD (arg=0x639cbc <wsrep_replication_process(THD*)>) at /media/Tintin/Work/code/percona-xtradb-cluster/pxc56/Percona-Server/sql/mysqld.cc:5380
        thd = 0x7fcfcc0009a0
        processor = 0x639cbc <wsrep_replication_process(THD*)>
#21 0x00007fcff47ef0a2 in start_thread () from /usr/lib/libpthread.so.0
No symbol table info available.
#22 0x00007fcff2c3443d in clone () from /usr/lib/libc.so.6
No symbol table info available.
quit


================================================================

Is this related to "  msg = "Failed to apply app buffer: seqno: 176, status: 1\n\t at galera/src/trx_handle.cpp:apply():333", 
"  in the bt above?