I have the same problem though it doesn't crash every time.

Application: akonadi_kalarm_resource (4.89.0)

Qt Version: 5.4.2
Operating System: Linux 4.2.0-19-generic x86_64
Distribution: Ubuntu 15.10

-- Backtrace:
Application: Akonadi Resource (akonadi_kalarm_resource), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f9aa9b65840 (LWP 2413))]

Thread 2 (Thread 0x7f9aa78c8700 (LWP 2428)):
#0  0x00007f9ab99f78dd in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f9ab1cd6bd2 in poll (__timeout=-1, __nfds=1, __fds=0x7f9aa78c7c80) at /usr/include/x86_64-linux-gnu/bits/poll2.h:46
#2  _xcb_conn_wait (c=c@entry=0x1e751f0, cond=cond@entry=0x1e75230, vector=vector@entry=0x0, count=count@entry=0x0) at ../../src/xcb_conn.c:459
#3  0x00007f9ab1cd874f in xcb_wait_for_event (c=0x1e751f0) at ../../src/xcb_in.c:623
#4  0x00007f9aa97efa39 in QXcbEventReader::run (this=0x1e73940) at qxcbconnection.cpp:1105
#5  0x00007f9aba3012be in QThreadPrivate::start (arg=0x1e73940) at thread/qthread_unix.cpp:337
#6  0x00007f9ab4b4d6aa in start_thread (arg=0x7f9aa78c8700) at pthread_create.c:333
#7  0x00007f9ab9a02eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7f9aa9b65840 (LWP 2413)):
[KCrash Handler]
#6  0x000000000041f257 in KAlarmResource::writeToFile (this=this@entry=0x1ecaca0, fileName=...) at ../../../../resources/kalarm/kalarm/kalarmresource.cpp:250
#7  0x0000000000414861 in Akonadi::SingleFileResource<Akonadi_KAlarm_Resource::Settings>::writeFile (this=0x1ecaca0, taskContext=<optimized out>) at ../../../../resources/shared/singlefileresource/singlefileresource.h:257
#8  0x00007f9abcc9054d in Akonadi::SingleFileResourceBase::qt_static_metacall (_o=_o@entry=0x1ecaca0, _c=_c@entry=QMetaObject::InvokeMetaMethod, _id=_id@entry=5, _a=_a@entry=0x7ffd0147ca30) at moc_singlefileresourcebase.cpp:107
#9  0x00007f9aba4ebc02 in QMetaMethod::invoke (this=this@entry=0x7ffd0147cc18, object=object@entry=0x1ecaca0, connectionType=Qt::DirectConnection, connectionType@entry=21482656, returnValue=..., val0=..., val1=..., val2=..., val3=..., val4=..., val5=..., val6=..., val7=..., val8=..., val9=...) at kernel/qmetaobject.cpp:2183
#10 0x00007f9aba4f0d2d in QMetaObject::invokeMethod (obj=0x1ecaca0, member=0x1ea6608 "writeFile", type=21482656, type@entry=Qt::AutoConnection, ret=..., val0=..., val1=..., val2=..., val3=..., val4=..., val5=..., val6=..., val7=..., val8=..., val9=...) at kernel/qmetaobject.cpp:1478
#11 0x00007f9abca57ae1 in QMetaObject::invokeMethod (val9=..., val8=..., val7=..., val6=..., val5=..., val4=..., val3=..., val2=..., val1=..., val0=..., member=<optimized out>, obj=<optimized out>) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qobjectdefs.h:407
#12 Akonadi::ResourceScheduler::executeNext (this=0x1f6e1c0) at ../../../../akonadi/src/agentbase/resourcescheduler.cpp:393
#13 0x00007f9abca58435 in Akonadi::ResourceScheduler::qt_static_metacall (_o=<optimized out>, _c=<optimized out>, _id=<optimized out>, _a=<optimized out>) at ./moc_resourcescheduler_p.cpp:175
#14 0x00007f9aba512651 in QObject::event (this=0x1f6e1c0, e=<optimized out>) at kernel/qobject.cpp:1245
#15 0x00007f9abb4ecb8c in QApplicationPrivate::notify_helper (this=this@entry=0x1e67400, receiver=receiver@entry=0x1f6e1c0, e=e@entry=0x1fb7480) at kernel/qapplication.cpp:3720
#16 0x00007f9abb4f2230 in QApplication::notify (this=0x7ffd0147d6f0, receiver=0x1f6e1c0, e=0x1fb7480) at kernel/qapplication.cpp:3503
#17 0x00007f9aba4e0f1b in QCoreApplication::notifyInternal (this=0x7ffd0147d6f0, receiver=0x1f6e1c0, event=event@entry=0x1fb7480) at kernel/qcoreapplication.cpp:935
#18 0x00007f9aba4e3057 in QCoreApplication::sendEvent (event=0x1fb7480, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:228
#19 QCoreApplicationPrivate::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0, data=0x1e5eac0) at kernel/qcoreapplication.cpp:1552
#20 0x00007f9aba4e3588 in QCoreApplication::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0) at kernel/qcoreapplication.cpp:1410
#21 0x00007f9aba537e73 in postEventSourceDispatch (s=0x1ebc4d0) at kernel/qeventdispatcher_glib.cpp:271
#22 0x00007f9ab462dff7 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#23 0x00007f9ab462e250 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#24 0x00007f9ab462e2fc in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#25 0x00007f9aba53827f in QEventDispatcherGlib::processEvents (this=0x1eb01a0, flags=...) at kernel/qeventdispatcher_glib.cpp:418
#26 0x00007f9aba4de75a in QEventLoop::exec (this=this@entry=0x7ffd0147d660, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#27 0x00007f9aba4e62cc in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1188
#28 0x00007f9ab903d00c in QGuiApplication::exec () at kernel/qguiapplication.cpp:1510
#29 0x00007f9abb4e9025 in QApplication::exec () at kernel/qapplication.cpp:2956
#30 0x00007f9abca4421a in Akonadi::ResourceBase::init (r=r@entry=0x1ecaca0) at ../../../../akonadi/src/agentbase/resourcebase.cpp:602
#31 0x00000000004209c8 in Akonadi::ResourceBase::init<KAlarmResource> (argc=<optimized out>, argv=<optimized out>) at /usr/include/KF5/AkonadiAgentBase/resourcebase.h:193
#32 0x00007f9ab991ca40 in __libc_start_main (main=0x411b40 <main(int, char**)>, argc=3, argv=0x7ffd0147d818, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffd0147d808) at libc-start.c:289
#33 0x0000000000411b79 in _start ()

*** This bug has been marked as a duplicate of bug 354417 ***