Seems to be some problem when accessing System information from multiple threads. Can't find anywhere that this is not supported. Creating a QSystemDeviceInfo in main thread and then create another thread that creates a QSystemNetworkInfo it will crash. However if you create and delete QSystemNetworkInfo in main thread it will work to create it in the other thread but then some signals fail to be sent (maybe another issue).
Think this could be due to that some static members are created first time the QSystemDeviceInfo/QSystemNetworkInfo is created.
Posted a simple application that will crash. But will work if you uncomment one line in MainWindow.cpp. Note that it can't be signed with self-signed as it needs QSystemNetworkInfo.