Repeating Timer does not fire events if no other event occurs

I was trying the Animation example https://lorensen.github.io/VTKExamples/site/Cxx/Utilities/Animation/

and it seems as the RepeatingTimer does only fire events when i hover the mouse over the window. When i stop the mouse at the window it stops firing the events.

Does someone has any idea on that ?

I am running vtk on a ubuntu 18.04.4 LTS with gcc 7.5.0