The resource regular crashes after approximately half an hour.
See backtrace:

Application: Akonadi Resource (akonadi_kolab_resource), signal: Aborted
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f067f3f2800 (LWP 12620))]

Thread 3 (Thread 0x7f0676017700 (LWP 12623)):
#0  g_mutex_unlock (mutex=0x7f0670000990) at /build/glib2.0-NiYzoW/glib2.0-2.44.1/./glib/gthread-posix.c:1348
#1  0x00007f0685179d6d in g_main_context_iterate (context=context@entry=0x7f0670000990, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/glib2.0-NiYzoW/glib2.0-2.44.1/./glib/gmain.c:3756
#2  0x00007f0685179fcc in g_main_context_iteration (context=0x7f0670000990, may_block=1) at /build/glib2.0-NiYzoW/glib2.0-2.44.1/./glib/gmain.c:3869
#3  0x00007f068dff5fbb in QEventDispatcherGlib::processEvents (this=0x7f06700008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:420
#4  0x00007f068df79962 in QEventLoop::processEvents (this=0x7f0676016d60, flags=...) at kernel/qeventloop.cpp:128
#5  0x00007f068df79c3b in QEventLoop::exec (this=0x7f0676016d60, flags=...) at kernel/qeventloop.cpp:204
#6  0x00007f068dcfd80e in QThread::exec (this=0x1ac2080) at thread/qthread.cpp:503
#7  0x00007f068dcfd9b0 in QThread::run (this=0x1ac2080) at thread/qthread.cpp:570
#8  0x00007f068dd04d39 in QThreadPrivate::start (arg=0x1ac2080) at thread/qthread_unix.cpp:337
#9  0x00007f0694f2b0a4 in start_thread (arg=0x7f0676017700) at pthread_create.c:309
#10 0x00007f068d16804d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 2 (Thread 0x7f0675816700 (LWP 6817)):
#0  0x00007f068d15f50d in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f0685179ebc in g_main_context_poll (priority=2147483647, n_fds=1, fds=0x7f0668003170, timeout=-1, context=0x7f06680030b0) at /build/glib2.0-NiYzoW/glib2.0-2.44.1/./glib/gmain.c:4103
#2  g_main_context_iterate (context=context@entry=0x7f06680030b0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/glib2.0-NiYzoW/glib2.0-2.44.1/./glib/gmain.c:3803
#3  0x00007f0685179fcc in g_main_context_iteration (context=0x7f06680030b0, may_block=1) at /build/glib2.0-NiYzoW/glib2.0-2.44.1/./glib/gmain.c:3869
#4  0x00007f068dff5fbb in QEventDispatcherGlib::processEvents (this=0x7f0668003570, flags=...) at kernel/qeventdispatcher_glib.cpp:420
#5  0x00007f068df79962 in QEventLoop::processEvents (this=0x7f0675815d60, flags=...) at kernel/qeventloop.cpp:128
#6  0x00007f068df79c3b in QEventLoop::exec (this=0x7f0675815d60, flags=...) at kernel/qeventloop.cpp:204
#7  0x00007f068dcfd80e in QThread::exec (this=0x1ae9f20) at thread/qthread.cpp:503
#8  0x00007f068dcfd9b0 in QThread::run (this=0x1ae9f20) at thread/qthread.cpp:570
#9  0x00007f068dd04d39 in QThreadPrivate::start (arg=0x1ae9f20) at thread/qthread_unix.cpp:337
#10 0x00007f0694f2b0a4 in start_thread (arg=0x7f0675816700) at pthread_create.c:309
#11 0x00007f068d16804d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 1 (Thread 0x7f067f3f2800 (LWP 12620)):
[KCrash Handler]
#6  0x00007f068d0b7107 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#7  0x00007f068d0b84e8 in __GI_abort () at abort.c:89
#8  0x00007f068d0f5204 in __libc_message (do_abort=do_abort@entry=1, fmt=fmt@entry=0x7f068d1e7fe0 "*** Error in `%s': %s: 0x%s ***\n") at ../sysdeps/posix/libc_fatal.c:175
#9  0x00007f068d0fa9de in malloc_printerr (action=1, str=0x7f068d1e81a0 "free(): invalid next size (fast)", ptr=<optimized out>) at malloc.c:4996
#10 0x00007f068d0fb6e6 in _int_free (av=<optimized out>, p=<optimized out>, have_lock=0) at malloc.c:3840
#11 0x00000000004bfd1c in Akonadi::ImapAclAttribute::~ImapAclAttribute (this=0x1aa3890, __in_chrg=<optimized out>) at /opt/kde/src/kde/kdepim-runtime/resources/shared/singlefileresource/imapaclattribute.h:33
#12 0x00007f0698292cf5 in qDeleteAll<QHash<QByteArray, Akonadi::Attribute*>::const_iterator> (begin=..., end=...) at /opt/qt5/qtbase/include/QtCore/qalgorithms.h:315
#13 0x00007f0698292451 in qDeleteAll<QHash<QByteArray, Akonadi::Attribute*> > (c=...) at /opt/qt5/qtbase/include/QtCore/qalgorithms.h:323
#14 0x00007f06982aa5ed in Akonadi::EntityPrivate::~EntityPrivate (this=0x1a90840, __in_chrg=<optimized out>) at /opt/kde/src/kde/kdepimlibs/akonadi/src/core/entity_p.h:56
#15 0x00007f06982aae40 in Akonadi::CollectionPrivate::~CollectionPrivate (this=0x1a90840, __in_chrg=<optimized out>) at /opt/kde/src/kde/kdepimlibs/akonadi/src/core/collection_p.h:77
#16 0x00007f06982aae70 in Akonadi::CollectionPrivate::~CollectionPrivate (this=0x1a90840, __in_chrg=<optimized out>) at /opt/kde/src/kde/kdepimlibs/akonadi/src/core/collection_p.h:78
#17 0x00007f06982bcc21 in QSharedDataPointer<Akonadi::EntityPrivate>::~QSharedDataPointer (this=0x1b26d78, __in_chrg=<optimized out>) at /opt/qt5/qtbase/include/QtCore/qshareddata.h:80
#18 0x00007f06982bc1e4 in Akonadi::Entity::~Entity (this=0x1b26d78, __in_chrg=<optimized out>) at /opt/kde/src/kde/kdepimlibs/akonadi/src/core/entity.cpp:61
#19 0x00007f06982a915c in Akonadi::Collection::~Collection (this=0x1b26d78, __in_chrg=<optimized out>) at /opt/kde/src/kde/kdepimlibs/akonadi/src/core/collection.cpp:76
#20 0x00000000004d7e2e in RetrieveCollectionMetadataTask::~RetrieveCollectionMetadataTask (this=0x1b26d30, __in_chrg=<optimized out>) at /opt/kde/src/kde/kdepim-runtime/resources/imap/retrievecollectionmetadatatask.cpp:51
#21 0x00000000004d7e6a in RetrieveCollectionMetadataTask::~RetrieveCollectionMetadataTask (this=0x1b26d30, __in_chrg=<optimized out>) at /opt/kde/src/kde/kdepim-runtime/resources/imap/retrievecollectionmetadatatask.cpp:53
#22 0x00007f068dfc1c54 in qDeleteInEventHandler (o=0x1b26d30) at kernel/qobject.cpp:4391
#23 0x00007f068dfb9670 in QObject::event (this=0x1b26d30, e=0x1a9c1b0) at kernel/qobject.cpp:1236
#24 0x00007f068eac468c in QApplicationPrivate::notify_helper (this=0x199a760, receiver=0x1b26d30, e=0x1a9c1b0) at kernel/qapplication.cpp:3720
#25 0x00007f068eac1e08 in QApplication::notify (this=0x7ffc890a4fa0, receiver=0x1b26d30, e=0x1a9c1b0) at kernel/qapplication.cpp:3164
#26 0x00007f068df7ccbe in QCoreApplication::notifyInternal (this=0x7ffc890a4fa0, receiver=0x1b26d30, event=0x1a9c1b0) at kernel/qcoreapplication.cpp:935
#27 0x00007f068df8091f in QCoreApplication::sendEvent (receiver=0x1b26d30, event=0x1a9c1b0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:228
#28 0x00007f068df7dff7 in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x196eb10) at kernel/qcoreapplication.cpp:1552
#29 0x00007f068df7d9a6 in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1410
#30 0x00007f068dff57e0 in postEventSourceDispatch (s=0x19db090) at kernel/qeventdispatcher_glib.cpp:271
#31 0x00007f0685179c3d in g_main_dispatch (context=0x7f0678002450) at /build/glib2.0-NiYzoW/glib2.0-2.44.1/./glib/gmain.c:3122
#32 g_main_context_dispatch (context=context@entry=0x7f0678002450) at /build/glib2.0-NiYzoW/glib2.0-2.44.1/./glib/gmain.c:3737
#33 0x00007f0685179f20 in g_main_context_iterate (context=context@entry=0x7f0678002450, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/glib2.0-NiYzoW/glib2.0-2.44.1/./glib/gmain.c:3808
#34 0x00007f0685179fcc in g_main_context_iteration (context=0x7f0678002450, may_block=1) at /build/glib2.0-NiYzoW/glib2.0-2.44.1/./glib/gmain.c:3869
#35 0x00007f068dff5f9b in QEventDispatcherGlib::processEvents (this=0x19d8720, flags=...) at kernel/qeventdispatcher_glib.cpp:418
#36 0x00007f067f1d43ce in QPAEventDispatcherGlib::processEvents (this=0x19d8720, flags=...) at eventdispatchers/qeventdispatcher_glib.cpp:115
#37 0x00007f068df79962 in QEventLoop::processEvents (this=0x7ffc890a4eb0, flags=...) at kernel/qeventloop.cpp:128
#38 0x00007f068df79c3b in QEventLoop::exec (this=0x7ffc890a4eb0, flags=...) at kernel/qeventloop.cpp:204
#39 0x00007f068df7d398 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1188
#40 0x00007f068e37fdb0 in QGuiApplication::exec () at kernel/qguiapplication.cpp:1507
#41 0x00007f068eac1635 in QApplication::exec () at kernel/qapplication.cpp:2956
#42 0x00007f0693f1ea48 in Akonadi::ResourceBase::init (r=0x1a47640) at /opt/kde/src/kde/kdepimlibs/akonadi/src/agentbase/resourcebase.cpp:589
#43 0x00000000004ac4ac in Akonadi::ResourceBase::init<KolabResource> (argc=3, argv=0x7ffc890a50f8) at /opt/kde/install/kf5/include/KF5/AkonadiAgentBase/resourcebase.h:192
#44 0x00000000004ab49b in main (argc=3, argv=0x7ffc890a50f8) at /opt/kde/src/kde/kdepim-runtime/resources/kolab/kolabresource.cpp:181