Trying to plug in a second monitor, I get a SIGSEGV.

I installed a debug version of the qt5-declarative package in the hope that the coredump provides at least something useful. How can I help to debug this further?

> coredumpctl gdb 5010
           PID: 5010 (plasmashell)
           UID: 1000 (artjom)
           GID: 100 (users)
        Signal: 11 (SEGV)
     Timestamp: Di 2016-10-11 21:55:55 CEST (1min 10s ago)
  Command Line: plasmashell --shut-up
    Executable: /usr/bin/plasmashell
 Control Group: /user.slice/user-1000.slice/session-c2.scope
          Unit: session-c2.scope
         Slice: user-1000.slice
       Session: c2
     Owner UID: 1000 (artjom)
       Boot ID: 603b3c155c0b46b88c57abd121e228b2
    Machine ID: 7bdb0655a4fb419e8414f89b1776261e
      Hostname: linux.laptop
      Coredump: /var/lib/systemd/coredump/core.plasmashell.1000.603b3c155c0b46b88c57abd121e228b2.5010.1476215755000000000000.lz4
       Message: Process 5010 (plasmashell) of user 1000 dumped core.
                
                Stack trace of thread 5010:
                #0  0x00007f3054d7761c CallMethod (libQt5Qml.so.5)
                #1  0x00007f3054d797b5 CallPrecise (libQt5Qml.so.5)
                #2  0x00007f3054d7a34d _ZNK3QV413QObjectMethod12callInternalEPNS_8CallDataE (libQt5Qml.so.5)
                #3  0x00007f3054d8f730 _ZNK3QV46Object4callEPNS_8CallDataE (libQt5Qml.so.5)
                #4  0x00007f30310f95ea n/a (n/a)

btGNU gdb (GDB) 7.11.1
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /usr/bin/plasmashell...(no debugging symbols found)...done.
[New LWP 5010]
[New LWP 5023]
[New LWP 5127]
[New LWP 5137]
[New LWP 5248]
[New LWP 5136]
[New LWP 5201]
[New LWP 5100]
[New LWP 5067]
[New LWP 5200]

warning: Could not load shared library symbols for linux-vdso.so.1.
Do you need "set solib-search-path" or "set sysroot"?
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
Core was generated by `plasmashell --shut-up'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  CallMethod (object=..., index=19, returnType=returnType@entry=6, argCount=1, argTypes=0x66277c4, engine=engine@entry=0x24a7220, callArgs=0x7f3032bb65b0)
    at /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-opensource-src-5.7.0/src/qml/jsruntime/qv4qobjectwrapper.cpp:1116
1116    /tmp/makepkg/qt5-declarative-debug/src/qtdeclarative-opensource-src-5.7.0/src/qml/jsruntime/qv4qobjectwrapper.cpp: Datei oder Verzeichnis nicht gefunden.
[Current thread is 1 (Thread 0x7f3057cc8800 (LWP 5010))]

Reproducible: Sometimes

Steps to Reproduce:
1. On a Dell XPS 13 (9350), plug in an external monitor through a USB 3.1 type C converter/adapter <-> HDMI cable
2. Watch plasmashell crash in 50% of the cases