A mysterious crash bug

My app built with Qt has been having random crash that I can't re-produce on macOS. It started since I upgraded from Qt 5.7.1 to Qt 5.9.6 and also Qt 5.11.2. I myself have not experienced the crash but at least 5 users of my app has send me this same crash report:

Thread 26 Crashed:
0   libsystem_kernel.dylib         0x00007fff6f8bcb86 __pthread_kill + 10
1   libsystem_pthread.dylib        0x00007fff6f972c50 pthread_kill + 285
2   libsystem_c.dylib              0x00007fff6f8261c9 abort + 127
3   org.qt-project.QtCore          0x000000010e04cf79 0x10e036000 + 94073
4   org.qt-project.QtCore          0x000000010e04e8f0 QMessageLogger::fatal(char const*, ...) const + 224
5   org.qt-project.QtCore          0x000000010e274ecd QEventDispatcherUNIXPrivate::QEventDispatcherUNIXPrivate() + 221
6   org.qt-project.QtCore          0x000000010e2757a5 QEventDispatcherUNIX::QEventDispatcherUNIX(QObject*) + 37
7   org.qt-project.QtCore          0x000000010e061e21 0x10e036000 + 179745
8   org.qt-project.QtCore          0x000000010e061f33 0x10e036000 + 180019
9   libsystem_pthread.dylib        0x00007fff6f97033d _pthread_body + 126
10  libsystem_pthread.dylib        0x00007fff6f9732a7 _pthread_start + 70
11  libsystem_pthread.dylib        0x00007fff6f96f425 thread_start + 13
 
It happens with Qt 5.9.6 and Qt 5.11.2, under macOS 10.13.6 and 10.14. I'm really puzzled by it and do not know how to proceed. Is this something that you guys have experienced before?