Phalcon + nginx + php7.1-fpm crashed with signal 11

I'm writing a website with Phalconphp, everything is good until I have to save comments into database. Anytime I call save() or create() method on any models, my php7.1-fpm crashed with following log in /var/log/php7.1-fpm.log

[25-Jan-2018 11:45:31] WARNING: [pool www] child 4277 exited on signal 11 (SIGSEGV - core dumped) after 14.239844 seconds from start
[25-Jan-2018 11:45:31] NOTICE: [pool www] child 4290 started

I tried to use gdb to debug, here is the result (in the IndexController/indexAction() I made a save() call on a model):

gdb php7.1
run index.php
Starting program: /usr/bin/php7.1 index.php
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
strlen () at ../sysdeps/x86_64/strlen.S:106
106     ../sysdeps/x86_64/strlen.S: No such file or directory.

And run bt full:

(gdb) bt full
\#0  strlen () at ../sysdeps/x86_64/strlen.S:106
No locals.
\#1  0x000055555575cd49 in ?? ()
No symbol table info available.
\#2  0x000055555575dfb8 in vspprintf ()
No symbol table info available.
\#3  0x0000555555630826 in ?? ()
No symbol table info available.
\#4  0x000055555563283e in zend_error_noreturn ()
No symbol table info available.
\#5  0x00007fffe819f967 in zephir_array_fetch_long.isra () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#6  0x00007fffe840f41b in zim_Phalcon_Mvc_Model_MetaData_readMetaDataIndex () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#7  0x00005555557ad086 in zend_call_function ()
No symbol table info available.
\#8  0x00007fffe81a051b in zephir_call_user_function () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#9  0x00007fffe81a0e9a in zephir_call_class_method_aparams.part () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#10 0x00007fffe81e247b in zim_Phalcon_Mvc_Model_MetaData_getBindTypes () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#11 0x00005555557ad086 in zend_call_function ()
No symbol table info available.
\#12 0x00007fffe81a051b in zephir_call_user_function () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#13 0x00007fffe81a0e9a in zephir_call_class_method_aparams.part () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#14 0x00007fffe83a1bf3 in zim_Phalcon_Mvc_Model\__exists () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#15 0x00005555557ad086 in zend_call_function ()
No symbol table info available.
\#16 0x00007fffe81a051b in zephir_call_user_function () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#17 0x00007fffe81a0e9a in zephir_call_class_method_aparams.part () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#18 0x00007fffe8317a5e in zim_Phalcon_Mvc_Model_save () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#19 0x0000555555860160 in ?? ()
No symbol table info available.
\#20 0x000055555580705b in execute_ex ()
No symbol table info available.
\#21 0x00005555557ad15b in zend_call_function ()
No symbol table info available.
\#22 0x00007fffe819d336 in zephir_call_user_func_array_noex () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#23 0x00007fffe8255b86 in zim_Phalcon_Dispatcher_callActionMethod () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#24 0x00005555557ad086 in zend_call_function ()
No symbol table info available.
\#25 0x00007fffe81a051b in zephir_call_user_function () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#26 0x00007fffe81a0e9a in zephir_call_class_method_aparams.part () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#27 0x00007fffe84654a4 in zim_Phalcon_Dispatcher_dispatch () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#28 0x00005555557ad086 in zend_call_function ()
No symbol table info available.
\#29 0x00007fffe81a051b in zephir_call_user_function () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#30 0x00007fffe81a0e9a in zephir_call_class_method_aparams.part () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#31 0x00007fffe83d94f0 in zim_Phalcon_Mvc_Application_handle () from /usr/lib/php/20160303/phalcon.so
No symbol table info available.
\#32 0x000055555585fc9c in ?? ()
---Type <return> to continue, or q <return> to quit---

Please give me help to address the problem. Thanks, Dat