in code QTitanRibbon-4.14.0 with Qt 5.8 by VS 2013 in win10 64bit platform.
When in single-selection mode, two tree item can be displayed as selection in QTreeWidget.
The method to re-produce this issue:
1: open the example project in the installation directory qtitanribbon.pro
2: use the OfficeStyleWIdgets project
3: change the following code as below:
QTreeWidget* treeWidget = new QTreeWidget;
// Comments out
// Switch it to single selection mode
and then build and run it, and try to select the different tree items many times, you will see two items are displayed as selection in UI. In the attached picture, the item2 and Item4 get displayed as selection.