Able to reproduce with PXC 5.6.19, but once...when it failed and I have started again it didn't give error. 


root@deb-pxc56-1:~/sysbench/sysbench# mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.6.19-67.0-56-log Percona XtraDB Cluster (GPL), Release 25.6, wsrep_25.6.r4111

...
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show global variables like 'table_open_cache%';
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| table_open_cache           | 2000  |
| table_open_cache_instances | 8     |
+----------------------------+-------+
2 rows in set (0.00 sec)

mysql> quit
Bye
root@deb-pxc56-1:~/sysbench/sysbench# ./sysbench --test=/root/sysbench/sysbench/tests/db/insert_autoinc.lua --oltp-table-size=100000 --oltp-tables-count=1 --num-threads=32 --mysql-host=127.0.0.1 --mysql-user=root --mysql-password=root --mysql-port=3306 --report-interval=1 --max-requests=0 --max-time=0 run
WARNING: Both max-requests and max-time are 0, running endless test
sysbench 0.5:  multi-threaded system evaluation benchmark

Running the test with following options:
Number of threads: 32
Report intermediate results every 1 second(s)
Random number generator seed is 0 and will be ignored


Threads started!

ALERT: failed to execute MySQL query: `INSERT INTO sbtest1 (k, c, pad) VALUES (49870, '69429576205-87925969202-02408199676-02281819182-93380360381-84587501731-92830026416-93404212567-05243222892-12376805095', '12147864779-36258834409-01700703135-41171421152-05431759726')`:
ALERT: Error 1062 Duplicate entry '212495' for key 'PRIMARY'
FATAL: failed to execute function `event': (null)
[   1s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 50.67, response time: 600.80ms (95%)
root@deb-pxc56-1:~/sysbench/sysbench# 


root@deb-pxc56-1:~/sysbench/sysbench# ./sysbench --test=/root/sysbench/sysbench/tests/db/insert_autoinc.lua --oltp-table-size=100000 --oltp-tables-count=1 --num-threads=32 --mysql-host=127.0.0.1 --mysql-user=root --mysql-password=root --mysql-port=3306 --report-interval=1 --max-requests=0 --max-time=0 run
WARNING: Both max-requests and max-time are 0, running endless test
sysbench 0.5:  multi-threaded system evaluation benchmark

Running the test with following options:
Number of threads: 32
Report intermediate results every 1 second(s)
Random number generator seed is 0 and will be ignored

Threads started!

[   1s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 0.00, response time: 0.00ms (95%)
[   2s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 34.00, response time: 1686.45ms (95%)
[   3s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 18.00, response time: 831.84ms (95%)
[   4s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 32.00, response time: 1796.94ms (95%)
[   5s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 30.00, response time: 1146.91ms (95%)
[   6s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 2.00, response time: 1131.23ms (95%)
[   7s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 32.03, response time: 1821.85ms (95%)
[   8s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 14.00, response time: 1491.67ms (95%)
[   9s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 18.00, response time: 1489.44ms (95%)
[  10s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 24.00, response time: 1844.90ms (95%)
[  11s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 9.00, response time: 1810.43ms (95%)
[  12s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 31.00, response time: 1494.35ms (95%)
[  13s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 9.00, response time: 1897.55ms (95%)
[  14s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 23.00, response time: 1825.67ms (95%)
[  15s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 32.00, response time: 1479.22ms (95%)
[  16s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 1.00, response time: 1744.47ms (95%)
[  17s] threads: 32, tps: 0.00, reads/s: 0.00, writes/s: 31.00, response time: 1809.89ms (95%)