I managed to get some thread dumps and have a core file to dig into now. This is repeatable even with all simulators.
<code> Storage: /var/lib/systemd/coredump/core.kstars.1000.c0048f3823804ad9a6b2901b20c2a816.52633.1587425852000000000000.lz4
Message: Process 52633 (kstars) of user 1000 dumped core.
Stack trace of thread 52633:
#0 0x00005581ed16666c _ZN4Ekos7Manager17syncActiveDevicesEv (kstars)
#1 0x00005581ed170f44 _ZN4Ekos7Manager18processNewPropertyEPN4INDI8PropertyE (kstars)
#2 0x00007f62decf0a60 _ZN11QMetaObject8activateEP7QObjectiiPPv (libQt5Core.so.5)
#3 0x00005581ed05ad46 _ZN3ISD11GDInterface15propertyDefinedEPN4INDI8PropertyE (kstars)
#4 0x00005581ed0e9924 _ZN3ISD13GenericDevice16registerPropertyEPN4INDI8PropertyE (kstars)
#5 0x00005581ed0ee1af _ZN12INDIListener16registerPropertyEPN4INDI8PropertyE (kstars)
#6 0x00005581ed091074 _ZN12INDIListener18qt_static_metacallEP7QObjectN11QMetaObject4CallEiPPv (kstars)
#7 0x00007f62decf179a _ZN7QObject5eventEP6QEvent (libQt5Core.so.5)
#8 0x00007f62df76aab6 _ZN19QApplicationPrivate13notify_helperEP7QObjectP6QEvent (libQt5Widgets.so.5)
#9 0x00007f62df774150 _ZN12QApplication6notifyEP7QObjectP6QEvent (libQt5Widgets.so.5)
#10 0x00007f62decc63e8 _ZN16QCoreApplication15notifyInternal2EP7QObjectP6QEvent (libQt5Core.so.5)
#11 0x00007f62decc942b _ZN23QCoreApplicationPrivate16sendPostedEventsEP7QObjectiP11QThreadData (libQt5Core.so.5)
#12 0x00007f62ded1ba97 _ZL23postEventSourceDispatchP8_GSourcePFiPvES1_ (libQt5Core.so.5)
#13 0x00007f62dd2de570 g_main_context_dispatch (libglib-2.0.so.0)
#14 0x00007f62dd2de900 g_main_context_iterate.isra.0 (libglib-2.0.so.0)
#15 0x00007f62dd2de9a3 g_main_context_iteration (libglib-2.0.so.0)
#16 0x00007f62ded1b825 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5)
#17 0x00007f62decc51db _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5)
#18 0x00007f62deccd0b6 _ZN16QCoreApplication4execEv (libQt5Core.so.5)
#19 0x00005581ece3eb76 main (kstars)
#20 0x00007f62dd9871a3 __libc_start_main (libc.so.6)
#21 0x00005581ece6a0ee _start (kstars)
Stack trace of thread 52642:
#0 0x00007f62de46107a pthread_cond_timedwait@@GLIBC_2.3.2 (libpthread.so.0)
#1 0x00007f62deb1c7e9 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5)
#2 0x00007f62deb1c90b _ZN14QWaitCondition4waitEP6QMutexm (libQt5Core.so.5)
#3 0x00007f62deb1a623 _ZN17QThreadPoolThread3runEv (libQt5Core.so.5)
#4 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52636:
#0 0x00007f62dda56a3f __poll (libc.so.6)
#1 0x00007f62dd2de86e g_main_context_iterate.isra.0 (libglib-2.0.so.0)
#2 0x00007f62dd2debf3 g_main_loop_run (libglib-2.0.so.0)
#3 0x00007f62c782cfca gdbus_shared_thread_func (libgio-2.0.so.0)
#4 0x00007f62dd308022 g_thread_proxy (libglib-2.0.so.0)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52635:
#0 0x00007f62dda56a3f __poll (libc.so.6)
#1 0x00007f62dd2de86e g_main_context_iterate.isra.0 (libglib-2.0.so.0)
#2 0x00007f62dd2de9a3 g_main_context_iteration (libglib-2.0.so.0)
#3 0x00007f62dd2de9f1 glib_worker_main (libglib-2.0.so.0)
#4 0x00007f62dd308022 g_thread_proxy (libglib-2.0.so.0)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52637:
#0 0x00007f62dda56a3f __poll (libc.so.6)
#1 0x00007f62dd2de86e g_main_context_iterate.isra.0 (libglib-2.0.so.0)
#2 0x00007f62dd2de9a3 g_main_context_iteration (libglib-2.0.so.0)
#3 0x00007f62ded1b825 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5)
#4 0x00007f62decc51db _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5)
#5 0x00007f62deb15c45 _ZN7QThread4execEv (libQt5Core.so.5)
#6 0x00007f62defa1f6a _ZN22QDBusConnectionManager3runEv (libQt5DBus.so.5)
#7 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#8 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#9 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52652:
#0 0x00007f62de46107a pthread_cond_timedwait@@GLIBC_2.3.2 (libpthread.so.0)
#1 0x00007f62deb1c7e9 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5)
#2 0x00007f62deb1c90b _ZN14QWaitCondition4waitEP6QMutexm (libQt5Core.so.5)
#3 0x00007f62deb1a623 _ZN17QThreadPoolThread3runEv (libQt5Core.so.5)
#4 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52643:
#0 0x00007f62de46107a pthread_cond_timedwait@@GLIBC_2.3.2 (libpthread.so.0)
#1 0x00007f62deb1c7e9 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5)
#2 0x00007f62deb1c90b _ZN14QWaitCondition4waitEP6QMutexm (libQt5Core.so.5)
#3 0x00007f62deb1a623 _ZN17QThreadPoolThread3runEv (libQt5Core.so.5)
#4 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52662:
#0 0x00007f62dda5c1bd syscall (libc.so.6)
#1 0x00007f62deb19278 _Z24futexSemaphoreTryAcquireILb0EEbR19QBasicAtomicIntegerIyEii (libQt5Core.so.5)
#2 0x00007f62decf0846 _ZN11QMetaObject8activateEP7QObjectiiPPv (libQt5Core.so.5)
#3 0x00005581ed05ac26 _ZN13ClientManager15newINDIPropertyEPN4INDI8PropertyE (kstars)
#4 0x00005581ed0d0bf3 _ZN13ClientManager11newPropertyEPN4INDI8PropertyE (kstars)
#5 0x00005581ed643d2f _ZN4INDI10BaseDevice9buildPropEP8xml_ele_Pc (kstars)
#6 0x00005581ed64840e _ZN4INDI10BaseClient15dispatchCommandEP8xml_ele_Pc (kstars)
#7 0x00005581ed648fb7 _ZN4INDI10BaseClient10listenINDIEv (kstars)
#8 0x00005581ed64914c _ZN4INDI10BaseClient12listenHelperEPv (kstars)
#9 0x00005581ed64918b _ZNSt6thread11_State_implINS_8_InvokerISt5tupleIJPFPvS3_EPN4INDI10BaseClientEEEEEE6_M_runEv (kstars)
#10 0x00007f62ddd603d4 execute_native_thread_routine (libstdc++.so.6)
#11 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#12 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52644:
#0 0x00007f62de46107a pthread_cond_timedwait@@GLIBC_2.3.2 (libpthread.so.0)
#1 0x00007f62deb1c7e9 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5)
#2 0x00007f62deb1c90b _ZN14QWaitCondition4waitEP6QMutexm (libQt5Core.so.5)
#3 0x00007f62deb1a623 _ZN17QThreadPoolThread3runEv (libQt5Core.so.5)
#4 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52651:
#0 0x00007f62de46107a pthread_cond_timedwait@@GLIBC_2.3.2 (libpthread.so.0)
#1 0x00007f62deb1c7e9 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5)
#2 0x00007f62deb1c90b _ZN14QWaitCondition4waitEP6QMutexm (libQt5Core.so.5)
#3 0x00007f62deb1a623 _ZN17QThreadPoolThread3runEv (libQt5Core.so.5)
#4 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52645:
#0 0x00007f62dda56a3f __poll (libc.so.6)
#1 0x00007f62dd2de86e g_main_context_iterate.isra.0 (libglib-2.0.so.0)
#2 0x00007f62dd2de9a3 g_main_context_iteration (libglib-2.0.so.0)
#3 0x00007f62ded1b825 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5)
#4 0x00007f62decc51db _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5)
#5 0x00007f62deb15c45 _ZN7QThread4execEv (libQt5Core.so.5)
#6 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#7 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#8 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52648:
#0 0x00007f62de46107a pthread_cond_timedwait@@GLIBC_2.3.2 (libpthread.so.0)
#1 0x00007f62deb1c7e9 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5)
#2 0x00007f62deb1c90b _ZN14QWaitCondition4waitEP6QMutexm (libQt5Core.so.5)
#3 0x00007f62deb1a623 _ZN17QThreadPoolThread3runEv (libQt5Core.so.5)
#4 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52653:
#0 0x00007f62de46107a pthread_cond_timedwait@@GLIBC_2.3.2 (libpthread.so.0)
#1 0x00007f62deb1c7e9 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5)
#2 0x00007f62deb1c90b _ZN14QWaitCondition4waitEP6QMutexm (libQt5Core.so.5)
#3 0x00007f62deb1a623 _ZN17QThreadPoolThread3runEv (libQt5Core.so.5)
#4 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52634:
#0 0x00007f62dda56a3f __poll (libc.so.6)
#1 0x00007f62dc31038a _xcb_conn_wait (libxcb.so.1)
#2 0x00007f62dc311fea xcb_wait_for_event (libxcb.so.1)
#3 0x00007f62cd01cd48 _ZN14QXcbEventQueue3runEv (libQt5XcbQpa.so.5)
#4 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52650:
#0 0x00007f62de46107a pthread_cond_timedwait@@GLIBC_2.3.2 (libpthread.so.0)
#1 0x00007f62deb1c7e9 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5)
#2 0x00007f62deb1c90b _ZN14QWaitCondition4waitEP6QMutexm (libQt5Core.so.5)
#3 0x00007f62deb1a623 _ZN17QThreadPoolThread3runEv (libQt5Core.so.5)
#4 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
Stack trace of thread 52649:
#0 0x00007f62de46107a pthread_cond_timedwait@@GLIBC_2.3.2 (libpthread.so.0)
#1 0x00007f62deb1c7e9 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5)
#2 0x00007f62deb1c90b _ZN14QWaitCondition4waitEP6QMutexm (libQt5Core.so.5)
#3 0x00007f62deb1a623 _ZN17QThreadPoolThread3runEv (libQt5Core.so.5)
#4 0x00007f62deb16d96 _ZN14QThreadPrivate5startEPv (libQt5Core.so.5)
#5 0x00007f62de45a4e2 start_thread (libpthread.so.0)
#6 0x00007f62dda616a3 __clone (libc.so.6)
</code>
and from gdb:
#0 0x00005581ed16666c in Ekos::Manager::syncActiveDevices() ()
[Current thread is 1 (Thread 0x7f62da1668c0 (LWP 52633))]