Hello again,
I didn't have the chance to install the 5.5.9+dfsg-1ubuntu4.15, I installed the 5.5.9+dfsg-1ubuntu4.16 today, and I got the same error:

#0  zend_mm_remove_from_free_list (heap=0x7ff52bdbab80, mm_block=0x7ff51c8d3118)
    at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_alloc.c:837
#1  0x00007ff524aa0fec in _zend_mm_free_int (heap=0x7ff52bdbab80, p=0x7ff51c8d3128)
    at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_alloc.c:2105
#2  0x00007ff5248b4983 in apprentice_unmap (map=0x7ff52c0bd3d0)
    at /build/php5-sR4fhr/php5-5.5.9+dfsg/ext/fileinfo/libmagic/apprentice.c:499
#3  0x00007ff5248b49f5 in mlist_free (mlist=0x7ff51cb57af8) at /build/php5-sR4fhr/php5-5.5.9+dfsg/ext/fileinfo/libmagic/apprentice.c:530
#4  0x00007ff5248b57e1 in file_ms_free (ms=0x7ff52c172218) at /build/php5-sR4fhr/php5-5.5.9+dfsg/ext/fileinfo/libmagic/apprentice.c:444
#5  0x00007ff5248bdfba in magic_close (ms=<optimized out>) at /build/php5-sR4fhr/php5-5.5.9+dfsg/ext/fileinfo/libmagic/magic.c:256
#6  0x00007ff5248b3af5 in finfo_resource_destructor (rsrc=0x7ff52c1176c8) at /build/php5-sR4fhr/php5-5.5.9+dfsg/ext/fileinfo/fileinfo.c:194
#7  0x00007ff524ad8040 in list_entry_destructor (ptr=0x7ff52c1176c8) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_list.c:183
#8  0x00007ff524ad5e81 in zend_hash_del_key_or_index (ht=ht@entry=0x7ff52528c7b0 <executor_globals+624>, arKey=arKey@entry=0x0,
    nKeyLength=nKeyLength@entry=0, h=h@entry=193, flag=flag@entry=1) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_hash.c:532
#9  0x00007ff524ad8221 in _zend_list_delete (id=<optimized out>) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_list.c:57
#10 0x00007ff524ab84d0 in _zval_dtor (zvalue=0x7ff52c113df0) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_variables.h:35
#11 i_zval_ptr_dtor (zval_ptr=0x7ff52c113df0) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_execute.h:81
#12 _zval_ptr_dtor (zval_ptr=<optimized out>) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_execute_API.c:426
#13 0x00007ff524aea587 in zend_object_std_dtor (object=0x7ff52c117940) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_objects.c:54
#14 0x00007ff524aea5b9 in zend_objects_free_object_storage (object=0x7ff52c117940)
    at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_objects.c:137
#15 0x00007ff524af044c in zend_objects_store_del_ref_by_handle_ex (handle=296, handlers=<optimized out>)
    at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_objects_API.c:226
#16 0x00007ff524af0473 in zend_objects_store_del_ref (zobject=0x7ff52c117898)
    at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_objects_API.c:178
#17 0x00007ff524ab84d0 in _zval_dtor (zvalue=0x7ff52c117898) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_variables.h:35
#18 i_zval_ptr_dtor (zval_ptr=0x7ff52c117898) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_execute.h:81
#19 _zval_ptr_dtor (zval_ptr=<optimized out>) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_execute_API.c:426
#20 0x00007ff524ad5f88 in zend_hash_destroy (ht=0x7ff51cb65b00) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_hash.c:560
#21 0x00007ff524ac73fb in _zval_dtor_func (zvalue=0x7ff51cbae778) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_variables.c:45
#22 0x00007ff524ab84d0 in _zval_dtor (zvalue=0x7ff51cbae778) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_variables.h:35
#23 i_zval_ptr_dtor (zval_ptr=0x7ff51cbae778) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_execute.h:81
#24 _zval_ptr_dtor (zval_ptr=<optimized out>) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_execute_API.c:426
#25 0x00007ff524aea587 in zend_object_std_dtor (object=0x7ff51ce8ee10) at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_objects.c:54
#26 0x00007ff524aea5b9 in zend_objects_free_object_storage (object=0x7ff51ce8ee10)
    at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_objects.c:137
#27 0x00007ff524aeffb7 in zend_objects_store_free_object_storage (objects=objects@entry=0x7ff52528c8e0 <executor_globals+928>)
    at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_objects_API.c:97
#28 0x00007ff524ab8be3 in shutdown_executor () at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend_execute_API.c:293
#29 0x00007ff524ac83b2 in zend_deactivate () at /build/php5-sR4fhr/php5-5.5.9+dfsg/Zend/zend.c:935
#30 0x00007ff524a6874d in php_request_shutdown (dummy=dummy@entry=0x0) at /build/php5-sR4fhr/php5-5.5.9+dfsg/main/main.c:1808
#31 0x00007ff524b79faf in php_apache_request_dtor (r=<optimized out>)
    at /build/php5-sR4fhr/php5-5.5.9+dfsg/sapi/apache2handler/sapi_apache2.c:507
#32 php_handler (r=<optimized out>) at /build/php5-sR4fhr/php5-5.5.9+dfsg/sapi/apache2handler/sapi_apache2.c:679
#33 0x00007ff52b4fe830 in ap_run_handler (r=0x7ff51d4dc998) at config.c:169
#34 0x00007ff52b4fed79 in ap_invoke_handler (r=r@entry=0x7ff51d4dc998) at config.c:439
#35 0x00007ff52b513dfc in ap_internal_redirect (new_uri=<optimized out>, r=<optimized out>) at http_request.c:648
#36 0x00007ff52351ccfc in handler_redirect (r=0x7ff51d4df0a0) at mod_rewrite.c:5063
#37 0x00007ff52b4fe830 in ap_run_handler (r=0x7ff51d4df0a0) at config.c:169
#38 0x00007ff52b4fed79 in ap_invoke_handler (r=r@entry=0x7ff51d4df0a0) at config.c:439
#39 0x00007ff52b51433a in ap_process_async_request (r=0x7ff51d4df0a0) at http_request.c:317
#40 0x00007ff52b514614 in ap_process_request (r=r@entry=0x7ff51d4df0a0) at http_request.c:363
#41 0x00007ff52b5110b2 in ap_process_http_sync_connection (c=0x7ff52b2ad290) at http_core.c:190
#42 ap_process_http_connection (c=0x7ff52b2ad290) at http_core.c:231
#43 0x00007ff52b507e70 in ap_run_process_connection (c=0x7ff52b2ad290) at connection.c:41
#44 0x00007ff52b508258 in ap_process_connection (c=c@entry=0x7ff52b2ad290, csd=<optimized out>) at connection.c:202
#45 0x00007ff525d68767 in child_main (child_num_arg=child_num_arg@entry=4) at prefork.c:704
#46 0x00007ff525d689a6 in make_child (s=0x7ff52b46cde0, slot=slot@entry=4) at prefork.c:800
#47 0x00007ff525d68a06 in startup_children (number_to_start=1) at prefork.c:818
#48 0x00007ff525d696e0 in prefork_run (_pconf=<optimized out>, plog=0x7ff52b468028, s=0x7ff52b46cde0) at prefork.c:976
#49 0x00007ff52b4e56de in ap_run_mpm (pconf=0x7ff52b49b028, plog=0x7ff52b468028, s=0x7ff52b46cde0) at mpm_common.c:96
#50 0x00007ff52b4dee76 in main (argc=3, argv=0x7fff6d47d6a8) at main.c:777

more info:
php5:
PHP 5.5.9-1ubuntu4.16 (cli) (built: Apr 20 2016 14:31:27)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2014 Zend Technologies

apache2:
Server version: Apache/2.4.7 (Ubuntu)
Server built:   Mar 10 2015 13:05:59

ubuntu:
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.1 LTS"