Selected Item losing Highlight in QTableView

Hello Guys,

I have a problem with the extendedSelection of my QTableView.
The Problem is that i have some whitespace around my columns and rows and when i click this whitespace the highlighting of my selected Fields is lost.
Its not ocurring when i click somewhere else in my application, only in the whitespace.
Also when i set the selection mode to SingleSelection it works just fine.

here is a short gif to illustrate the problem
https://gyazo.com/8e4ae161aaff25a4afa1b588579ddd01

thank you everyone who can help me
sincerely