Crash on "setEnabled(false)"

Hi,

the Basic situation is a bit complicated to describe. I am creating a QDialog-Derrived class. This Dialog contains a QTabWnd, and this TabWnd a Layout with a QComboBox.  

Between construction of the dialog object, and the QDialog.exec() call, I have to disable the QComboBox under certain circumstances. Unfortunately the call to "setEnabled(false)" causes the emiting of a changeEvent that triggers an update of the accessibility. 

As far as I can debug into the QT source the creation of a QAccessibliScrollBar failes, or causes the free of invalid memory. Unfortunatels, this happens not always. I have no idea, what causes this problem and how I can solve/workaround this. Extended searching of the internet also gave no result. 

I have attached a crashdump of the problem that may help you to get to the point of interest and help me find out, whats happening. 

I am using MS Visual Studio 2015 with QT 5.12.2 x64 Dll pre-build binares provided by you,.

Best regards,

Marcel