I cannot reproduce this problem here.

Is this reproducible on your system? I.e. you start QCAD, you click on "Draw Order" in the property editor -> System stalls?

If not, your click on "Draw Order" very likely just coincided with a scheduled autosave (see Edit > Application Preferences > Load/Save > Autosave).

Reproducible with a bit larger file, not with none (can't) or simple drawings.

Selected an entity, made change to a Specific Property eg. Lenght
Clicked on Draw Order
Click away
System hangs, CPU load max out
system restores after several seconds

Waited 10 counts after an autosave
Grabbed the screen while stalling

Result is the same closing all windows and other applications and unnecessary processes.

Included Grab
Included Drawing file
(Original was not drawn with QCAD)

Thanks. I still cannot quite reproduce that, but I do notice a slight hang (maybe 0.2s) when the focus moves away from the draw order property.

You can find a potential fix at:
https://raw.githubusercontent.com/qcad/qcad/master/scripts/Widgets/PropertyEditor/PropertyEditor.js

This file replaces the file scripts/Widgets/PropertyEditor/PropertyEditor.js in your QCAD installation directory.

Please provide feedback on the potential fix if possible.

Replacement by the provided file fixes the problem as far as i can check it for now.
I think you hit the nail on the head.
Regards

OK, great. Thanks!