The test case is non-deterministic, as it has a send. It fails on the 1st attempt for me, but it can vary on different machines/builds. Run with --repeat=N if it doesn't fail right away.
#7 0x00007f76abd40ee2 in __assert_fail () from /lib/x86_64-linux-gnu/libc.so.6
#8 0x000055a5efe9c4cd in row_log_table_low_redundant (rec=0x7f76a5860167 "", index=0x7f765c12d4a8, insert=true, old_pk=0x0, new_index=0x7f7650022ab8) at /data/src/bb-10.4-MDEV-17520/storage/innobase/row/row0log.cc:802
#9 0x000055a5efe9d393 in row_log_table_low (rec=0x7f76a5860167 "", index=0x7f765c12d4a8, offsets=0x7f76a5084bd0, insert=true, old_pk=0x0) at /data/src/bb-10.4-MDEV-17520/storage/innobase/row/row0log.cc:989
#10 0x000055a5efe9ea4e in row_log_table_insert (rec=0x7f76a5860167 "", index=0x7f765c12d4a8, offsets=0x7f76a5084bd0) at /data/src/bb-10.4-MDEV-17520/storage/innobase/row/row0log.cc:1432
#11 0x000055a5efe69d2b in row_ins_clust_index_entry_low (flags=0, mode=16386, index=0x7f765c12d4a8, n_uniq=0, entry=0x7f765c0b22e8, n_ext=0, thr=0x7f765c046158, dup_chk_only=false) at /data/src/bb-10.4-MDEV-17520/storage/innobase/row/row0ins.cc:2801
#12 0x000055a5efe6b2e0 in row_ins_clust_index_entry (index=0x7f765c12d4a8, entry=0x7f765c0b22e8, thr=0x7f765c046158, n_ext=0, dup_chk_only=false) at /data/src/bb-10.4-MDEV-17520/storage/innobase/row/row0ins.cc:3262
#13 0x000055a5efe6b796 in row_ins_index_entry (index=0x7f765c12d4a8, entry=0x7f765c0b22e8, thr=0x7f765c046158) at /data/src/bb-10.4-MDEV-17520/storage/innobase/row/row0ins.cc:3387
#14 0x000055a5efe6be6c in row_ins_index_entry_step (node=0x7f765c045f00, thr=0x7f765c046158) at /data/src/bb-10.4-MDEV-17520/storage/innobase/row/row0ins.cc:3555
#15 0x000055a5efe6c2a0 in row_ins (node=0x7f765c045f00, thr=0x7f765c046158) at /data/src/bb-10.4-MDEV-17520/storage/innobase/row/row0ins.cc:3698
#16 0x000055a5efe6caa0 in row_ins_step (thr=0x7f765c046158) at /data/src/bb-10.4-MDEV-17520/storage/innobase/row/row0ins.cc:3943
#17 0x000055a5efe8c59b in row_insert_for_mysql (mysql_rec=0x7f765c0b1070 "\375\006", prebuilt=0x7f765c0459e8, ins_mode=ROW_INS_NORMAL) at /data/src/bb-10.4-MDEV-17520/storage/innobase/row/row0mysql.cc:1460
#18 0x000055a5efd257e2 in ha_innobase::write_row (this=0x7f765c045238, record=0x7f765c0b1070 "\375\006") at /data/src/bb-10.4-MDEV-17520/storage/innobase/handler/ha_innodb.cc:8045
#19 0x000055a5efa03666 in handler::ha_write_row (this=0x7f765c045238, buf=0x7f765c0b1070 "\375\006") at /data/src/bb-10.4-MDEV-17520/sql/handler.cc:6238
#20 0x000055a5ef6a7547 in write_record (thd=0x7f765c000b00, table=0x7f765c044600, info=0x7f76a5085b80) at /data/src/bb-10.4-MDEV-17520/sql/sql_insert.cc:2022
#21 0x000055a5ef6a48cb in mysql_insert (thd=0x7f765c000b00, table_list=0x7f765c014ea0, fields=..., values_list=..., update_fields=..., update_values=..., duplic=DUP_ERROR, ignore=false) at /data/src/bb-10.4-MDEV-17520/sql/sql_insert.cc:1063
#22 0x000055a5ef6ead97 in mysql_execute_command (thd=0x7f765c000b00) at /data/src/bb-10.4-MDEV-17520/sql/sql_parse.cc:4732
#23 0x000055a5ef6f595e in mysql_parse (thd=0x7f765c000b00, rawbuf=0x7f765c014da8 "INSERT INTO t1 VALUES (6),(7),(8),(9)", length=37, parser_state=0x7f76a5086600, is_com_multi=false, is_next_command=false) at /data/src/bb-10.4-MDEV-17520/sql/sql_parse.cc:8092
#24 0x000055a5ef6e2c3c in dispatch_command (command=COM_QUERY, thd=0x7f765c000b00, packet=0x7f765c1381c1 "INSERT INTO t1 VALUES (6),(7),(8),(9)", packet_length=37, is_com_multi=false, is_next_command=false) at /data/src/bb-10.4-MDEV-17520/sql/sql_parse.cc:1851
#25 0x000055a5ef6e1660 in do_command (thd=0x7f765c000b00) at /data/src/bb-10.4-MDEV-17520/sql/sql_parse.cc:1396
#26 0x000055a5ef84d14e in do_handle_one_connection (connect=0x55a5f3ca4a70) at /data/src/bb-10.4-MDEV-17520/sql/sql_connect.cc:1402
#27 0x000055a5ef84ced2 in handle_one_connection (arg=0x55a5f3ca4a70) at /data/src/bb-10.4-MDEV-17520/sql/sql_connect.cc:1308
#28 0x000055a5efd043c8 in pfs_spawn_thread (arg=0x55a5f3d29df0) at /data/src/bb-10.4-MDEV-17520/storage/perfschema/pfs.cc:1862
#29 0x00007f76ad7fc494 in start_thread (arg=0x7f76a5087700) at pthread_create.c:333
#30 0x00007f76abdfd93f in clone () from /lib/x86_64-linux-gnu/libc.so.6