StyleSheets are not set correctly

I created a test app that illustrates the issue: qtbug_79545.tgz

Just press any of the buttons and it will turn all red press it again and depending on the Qt version it will turn all green or partly green partly red. Desired is to turn all green. The regression seems to be introduced with 5.12.3

Please see the Screenshots:

• compiled with Qt 5.12.2:
  
• compiled with 5.13:
  

Rumen

 
Here the corresponding thread from the forum: https://forum.qt.io/topic/108112/stylesheet-problem-with-qt-5-12-2