The issue is only reproducible on systems that support multitouch (like MS Surface).
It can be reproduced on Windows 8.1 and Windows 10 with all the latest updates installed.

Use attached test application to reproduce the issue.
The test application handles Touch and Mouse events.

Steps to reproduce the issue:
1. Tap on the combobox and let the menu stay open.
2. Tap on the rectangle below it.
-> Only QEvent::MouseButtonPress (2) is being triggered.

Expected outcome:
Normally, when the rectangle is being tapped the following events are being triggered:

194 
196 
2 
3

or any other combination of 194/196 2/3
It's expected that the same would happen even if the combobox menu is opened.